Can somebody summarize the different "branches" of Christianity to me, and explain why they exist in the first place?

What you are asking about is not so much the "main software product", but rather the "original" software product that many other similar software products come from - all claiming to be the original, it seems. So how do you know which is which?

When it comes to software, you will have to examine the source (code). The same is the case with Christianity. In order to really know it, you need to examine the source, which is the Bible. That is the only way you can really find an answer to your questions. I can only summarise answers here, because on each question there is much more to say.

1. So was Jesus a Jew?

Born an Israelite, descendant of Judah and David (Matthew 1:1,16-17), Jesus was circumcised according to the Law of Moses (Luke 2:21-24,41-42) and was as an adult generally recognised as a Jew (Luke 4:16; John 4:9).

2. Did Jesus start a new branch?

Upon asking the question who they thought he was, Jesus disciples appear in agreement believing that he was the promised Messiah (Matthew 16:14-16). However, Jesus' ransom sacrifice made a new covenant possible, that abolished (made obsolete) the old covenant, of which the Mosaic Law was a part (Luke 22:20,29; Romans 10:4, Hebrews 8:7-9,13). With this new covenant came a new law, known as the "Law of the Christ" (John 13:34, Galatians 6:2). Was Jesus authorised to do so? Yes, because he had fulfilled the Law, as in completing the contract (Mat. 5:17) and was approved and appointed as king of God's Kingdom [government] (Daniel 2:44, 7:13,14; Matthew 17:5; 18:28; 23:10; 1 Corinthians 11:3).

3. How many Bibles are there?

Jesus believed in one set of Scriptures as the inspired Word of God (Matthew 22:40), as did the apostles (Acts 15:15; 2 Timothy 3:16; 2 Peter 1:20-21). A large number of copies and various translations have been made, but the source is ultimately the same.

4. Does the Bible support and/or promote branches?

No, it does not. In fact, the apostle Paul explicitly urged to stay united (1 Corinthians 1:10; 1 Timothy 2:8; 2 Timothy 2:23,24) and when there was a division on the issue of circumcision, it was taken to the apostles in Jerusalem (Acts 15:1,2). A spirit-directed decision was made, keeping the unity in teaching among the congregations (Acts 15:22-31).

In addition, Jesus warned against imposters and false prophets (Matthew 7:15; 24:4,5) and the apostles warned against such ones trying to get a following for themselves (Acts 20:29,30; 1 Timothy 4:1; 1 John 4:1; Jude 4,17-19). In fact, in 2 Thessalonians 2:3,4 it is revealed that an apostacy was to come; a falling away of the majority. How else could such a "man of lawlessness" be in God's temple [place of or arrangement for worship] "publicly showing himself to be a god"?

So how do you know the true Christian faith? Jesus gave a number of hints, pointing out that his true disciples:

• search to do God's will (Matthew 7:21-23; 1 John 5:3);
• show love towards one another, just as Jesus had (John 13:35); and
• follow Jesus' instructions (John 15:14), even those that are not as popular, such as sharing and teaching the good news of the Kingdom (Matthew 24:14; 28:19-20; Romans 10:9,13-15).

I hope the above provides sufficient material to answer your questions on why these branches in Christianity exist.

Going through the above material, I hope it's clear that there are only two branches of Christianity, just as Jesus said there would be: either true or false (John 4:23,24). I found an interesting list of points that expands a bit further on what the Bible says of these true worshippers or, as the article calls it, "true religion", backed up with a number of Scriptures at https://www.jw.org/en/bible-teachings/questions/which-religion-is-true/ . For example, it lists:

• teachings based on the Bible, not human philosophy;
• no paid clergy;
• promotion of unselfish love;
• political neutrality and obedience to secular authorities; and
• religion as a way of life, not a set of rituals or formalities.

I know about "protestant", "catholic" and then there's something else in the "main three" which I probably "should know" by heart but I simply don't.

(Probably referring to Eastern Orthodox?)

And then there's also things like Mormons ("Latter Day Saints") and many other minor "variants".

Yup. Add to that, Jehovah's Witnesses, Seventh Day Adventists, and others. (I singled out those two because, like Mormons, they use writings that may be generally accepted by fewer of other mainline Protestant branches.)

It would be much simpler if there were just "Christians", "Muslims", "Jews", etc., but it's apparently not enough to be "Christian", because all the different groups of Christians will not approve of you unless you use their "variant".

This is not Christian-specific. Muslims have the Sunni (the larger group) and Shiite/Shia.

The Christian sacred texts (books from the "New Testament") contain multiple references to Jewish sects, probably most notably the Pharisees followed by the Sadducees, but there are others like Zealots. There were also Samaritans and Hellenists.

Within the Protestant branch, you have a group called "Christian Reformed". Some people there may be a "five point Calvinist" (using a term named after a famed theologian named Calvin), but others might just be a "four point Calvinist" because they don't accept all five points of the traditional 5 point Calvinists.

I mean, why would they exist if they all agreed to the same stuff anyway?

Right. Mostly. Umm... Err...

The truth is that many churches tend to want to have a denomination as part of their name. However, in many cases, the selected denomination ends up being little more than just a part of a name, especially after time and after a change like a new pastor. You end up having Baptist churches that are more Lutheran than they are Baptist, and you have Lutheran churches that are more Baptist than they are Lutheran.

How true that is can vary. For instance, the Seventh-Day Adventist church has a pretty centralized hierarchy, similar in structure to the Holy Roman Catholic church (the church you probably know of as the "Catholic" church). But even then, there can be branches like members of a Branch Davidian group that banded together in a famous fatal stand-off in Waco, TX.

Even within the churches, you will then have some people who are more serious about religion than other people, and among the people who are more serious about religion as a whole, you will find that some people place more importance on some teachings than others.

So, yes, it is true that the the Presbyterians and the Methodists may have some difference. But that doesn't mean that there is a ton of agreement even within a single denomination.

As an example: I remember going to Cornwall Church of God, and in a class for people interested in becoming official members of the church, people were being told that they are technically part of the "Church of God" denomination, but it was just a technicality. Years later, that church officially stopped being part of that denomination altogether.

That particular (rather large) church ended up becoming officially "non-denominational". Several churches have embraced that term for themselves, or "evangelical" (which basically means they evangelize, meaning they spread their beliefs. There is essentially no difference at all between "evangelical" or "non-denominational". But, for that matter, some of the other established denominations have been losing their distinctiveness too.

Some (a lot, in fact) even say that Jesus was a Jew

The first seventeen verses of the New Testament start with "The book of the genealogy of Jesus Christ, the son of David, the son of Abraham." That Jesus was a Jew is just not an item in wide dispute. If someone wished to contest such an established fact, then one would wonder how many other established facts would be similarly disputed. For instance, if they are so quick to toss out such uncontroversial text in the bible, what remaining parts of the bible would they embrace? There are usually much bigger opportunities for disagreement than that one.

So, yes, Christianity grew from Judaism. When many members of Judaism did not embrace the changes in religious understanding that were surrounding Jesus, then those who embraced Jesus became known as Christian. The others became known as "Orthodox Jews", although are often just called "Jews". From the Christian perspective, they follow God and so did the Jewish nation before the time from when Jesus was born, and Christianity is simply the correct continuation of the God-following people who were previously known as "Jews". But when the Orthodox Jews resisted the new understandings being taught by the Christians, the Christians happily accepted their new name because they didn't want to shy away from the name of Jesus Christ.

In fact, I have never heard of any Christians who refer to the "protestant Bible" or "catholic Bible" -- it's always just "the Bible" (by which they mean the old and the new testaments combined, I assume)

Actually, these definitely exist. In short: The Jews have their main scripture which contains the same books as the protestant's "Old Testament", although the books are typically arranged in a different order what what is found in the Christian bibles. Jews often have other holy writings, Midrash, which they also consider significant. Then, the next largest major collection may be the "Protestant Bible", which contains what we call the "New Testament". However, the Catholics typically also embrace the Deuterocanon, which provides another 15 "interstitial" books, containing pre-"New Testament" content (some of which may be after the "Old Testament" books.

Islam comes along and we get the Quran, which acknowledges the Jewish and Christian texts but does not endorse treating those older texts as having full accuracy. In a nutshell, Abraham had two sons, one of whom I will title the Son of Promise, through whom God's promises were made. The Jews say that the older son, Ishmael, was born from implementation of a rebellious plan, so the younger son Isaac is who the Jewish line follows. The Quran follows the older son, Ishmael.

Of course, then there are additional books, such as the Book of Morman used by the LDS church, Mary Baker Eddy's "Science & Health with Key to the Scriptures", and Seventh-Day Adventist's Ellen White who wrote the Conflict Series of books. Both Mary Baker Eddy and Ellen White are key women who wrote a bunch of material, and each had a publishing house essentially set up to help that author's material be further spread.

Then, there are the apocrypha - even more books that some people accept, and others don't. Undoubtedly, some apocrypha is known to have been dishonest about who wrote it. But which apocrypha? Is any of it trustworthy? There are some more questions that people may have different opinions about.

Does the Bible in itself talk about and name these branches, or were they created much later, long after the Bible had been finished and spread?

No. The bible does speak of a split between Peter and Paul, but those leaders resolved their differences (as recorded in the bible). As mentioned before, the bible mentions some of the Jewish branches that existed. There is some biblical prophecy that some people will interpret as referring to religious people being non-unified, but such interpretation may be rather non-universal, and the bible certainly doesn't provide names for all the various sects/denominations of Christianity.

I find that the more basic my questions are, the more vague are the answers.

Well, one way to remain accurate is to be vague. As you leave the realm of being vague, the specifics will often introduce details that will be less universally agreed upon. there are books that provide lots of specific details. People would call such writings "doctrine" that may be widely disagreed upon by other people who don't accept some of the same narrow teaching.

So if you ask broad questions, you're likely to get some vague answers. Fortunately, this website is likely to accept questions of both types (broad/vague and specific).

That's just about all I know, amazingly. (It's why I ask.)

I suppose that as you learn some more of the basic facts, you are likely to find there are yet other details that you don't know. Realize that continuing to ask questions is not a sign of lacking intelligence. Rather, such efforts to learn just indicate that you have not fully mastered all aspects of religion.

I’ve done my best to address three of your sub-questions:

1. Why do we have Christianity if Jesus was a Jew?

God has always called prophets to teach the inhabitants of the earth (His children). These teachings always focused on Jesus Christ (the Jehovah of the Old Testament, the Messiah of the New Testament) because only through Jesus Christ can we be saved from our sins. The purpose of the Law of Moses was to prepare God’s people (the Jews) to receive Christ. When Jesus came to the earth, he fulfilled the Law of Moses and introduced a higher law. He also established his church. This included calling apostles and giving them authority to preach in his name and administer with his power (such as baptizing and healing the sick). The Jews, having strayed from God’s gospel, did not recognize their promised Messiah and rejected Jesus Christ. Those who chose to follow Christ were baptized into his church and called themselves Christians.

2. If all Christians believe in the Bible, why are there some many different branches?

While most (if not all) branches of Christianity believe in the Bible, there are many interpretations of what certain things mean. When prophets were on the earth, they were able to interpret scripture because they had the power and authority of God to act in His name. Whenever prophets were killed, there was a period of confusion and a falling away from the truth. Many of the different branches of Christianity came about because Jesus’s apostles were rejected and killed (and therefore the authority and key truths of the gospel were lost).

3. Explain about The Church of Jesus Christ of Latter-day Saints

Basic beliefs: We believe that God is our Loving Heavenly Father and we are His Children. We believe that Jesus Christ is the Son of God, that he came to earth and suffered for our sins. As we follow Jesus Christ, we can find happiness and this life and one day return back to live with God (and our families) again.

Quick background of The Church of Jesus Christ of Latter-day Saints: Throughout history, God has repeatedly called prophets to teach His children. Prophets are given authority (the priesthood) by God and are called to preach repentance and teach the gospel. When Jesus Christ was on the earth, he established his church. This included calling apostles and giving them authority to preach in his name and administer with his power (such as baptizing and healing the sick). After Jesus died, Peter became the prophet (as instructed by the resurrected Jesus) and filled the vacancies in the 12 by calling and ordaining 2 new apostles. Unfortunately, Peter and the apostles were rejected and killed. Key teachings and priesthood authority were lost from the earth. This “falling away” was foretold by many prophets and other writers of the Bible. In 1820, God again called a prophet (Joseph Smith), gave him priesthood authority, and called him to preach repentance and teach the gospel of Jesus Christ. In one of many revelations to Joseph, Jesus instructed him to reestablish his Church on the earth and call it The Church of Jesus Christ of Latter-day Saints. This “restoration of all things” (Christ’s church being restored to the earth) was also foretold by many prophets and apostles. See https://www.comeuntochrist.org/beliefs/jesus-christ-church

The Book of Mormon: Members of The Church of Jesus Christ of Latter-day Saints believe the Bible (both Old and New Testaments) to be the word of God. We study it, teach from it, and use it in our lives. We also believe that God has revealed other scriptures through his modern-day prophets. The Book of Mormon is another testament of Jesus Christ and relates the account of God’s dealings with the ancient inhabitants of the Americas. Joseph Smith translated The Book of Mormon by the power of God. We use The Book of Mormon hand-in-hand with the Bible to help us come closer to God and Jesus Christ. See https://www.comeuntochrist.org/beliefs/book-of-mormon

Interesting question, but where to start? It’s a big ask! The Wikipedia diagram provided by depperm is a very useful illustration showing the timeline and emergence of the different major branches within Christianity. https://en.wikipedia.org/wiki/List_of_Christian_denominations_by_number_of_members

However, if “all” you want is a brief, easily understood overview or summary of the main branches within Christianity then allow me to partially quote from an article from a Protestant perspective:

The church started with a supernatural work of God in Jerusalem. About fifty days after Jesus’ resurrection, the Holy Spirit filled the disciples, and they were empowered to preach the gospel. Acts 2 records the results of the Spirit’s coming—three thousand people were saved that day, and the church had begun (verse 41). Since that time of unity and simplicity, Christianity has separated into various branches. Today, most scholars identify three major branches of Christianity: Catholicism, Orthodoxy, and Protestantism, which are subdivided into other branches. Sometimes Anglicanism is listed as a fourth branch; sometimes it is listed as part of Protestantism. Source: https://www.gotquestions.org/branches-of-Christianity.html

The article gives a brief historical overview of Roman Catholicism, Eastern Orthodoxy and Protestantism. The article concludes:

The doctrinal differences between Roman Catholicism and Eastern Orthodoxy are serious enough to have kept those two branches of Christianity separate for almost 1,000 years. The crucial differences between those two groups and Protestants are likewise substantial and far-reaching. Ultimately, there is only one church; the Body of Christ is made up of all those who by faith in Christ are born again and have the Holy Spirit indwelling them. “There is one body and one Spirit, just as you were called to one hope when you were called; one Lord, one faith, one baptism; one God and Father of all, who is over all and through all and in all” (Ephesians 4:4–6).

Another article I found explores the emergence of Protestantism.

The rise of denominations within the Christian faith can be traced back to the Protestant Reformation, the movement to “reform” the Roman Catholic Church during the 16th century, out of which four major divisions or traditions of Protestantism would emerge: Lutheran, Reformed, Anabaptist, and Anglican. From these four, other denominations grew over the centuries.

The article concludes:

The point of these divisions is never Christ as Lord and Savior, but rather honest differences of opinion by godly, albeit flawed, people seeking to honor God and retain doctrinal purity according to their consciences and their understanding of His Word. Source: https://www.gotquestions.org/denominations-Christian.html

For me, as a Christian of the Protestant persuasion, the only important issue is Christ Jesus and understanding who he REALLY is. A fascinating subject, with profound implications. Hope that helps!

The other answers here are good, but I'll try to directly address some questions with more detail. And this is the sort of question where a lot of answers are "it's complicated, and no one perspective is correct."

As you stated, there are three "main branches" of Christianity, with most branches and sub-branches claiming to be the one, holy, catholic, and apostolic church. In this context, "one" means that there is only one true churches (not multiple correct churches with differences), "holy" is self-explanatory, "catholic" is a a synonym for "universal" (meaning all-encompassing), and "apostolic" means following in the tradition of the apostles

1. Catholicism: ~1.3 billion followers. Catholics believe the pope has primacy in the Church handed down through the generations from the apostle Peter. The pope has the power to proclaim dogma (major beliefs) via papal infallibility (as instructed by Jesus), though this has only officially happened once (with Mary's Assumption). Not everything he says is automatically infallible, and decisions are deliberated among other clergy. There is a formal hierarchy which essentially only has bishops above priests above deacons; the pope and cardinals are special bishops. Split with the Eastern Orthodox Churches in 1054. Most Catholics are Roman Catholic, though there are many other rites (groups) that all agree on what they think is important.

2. Orthodoxy: ~350 million followers. Includes many Churches, but Eastern and Oriental (another word for eastern) are the largest (and rather unrelated) groups. Orthodox Churches generally have multiple high-ranking clergy (called autocephalous patriarchs, literally meaning that they are their own heads). The Ecumenical Patriarch is the first among 5 equal patriarchs, and the Coptic Pope of Alexandria fills a similar role in the Coptic Church (the second-largest Oriental Church). Split with the Catholic Church in 1054.

3. Protestantism: ~900 million followers. The widest variety of large groups under one of the 3 branches. Succeeded in gaining a foothold while protesting practices of the Catholic Church starting in the 16th century (though many attempts had been made previously, resulting in smaller schisms or reformers being crushed). Generally tend to reject supremacy of any clergy member over others (preferring local preachers, with governing bodies setting guidelines more than rules). Generally believe that faith alone saves humans from damnation, and that works (good deeds) should come from a faithful person, but are not required for salvation (in contrast to Catholic and Orthodox Churches).

Some other denominations do not fit well into these branches, such as the Church of Jesus Christ of Latter-day Saints (Mormons). Mormons have holy scriptures in addition to the Bible, which are rejected by all 3 main branches. The official stance of the Catholic Church (since they have one on everything) is that Mormon baptisms are invalid (despite accepting Protestant and Orthodox baptisms). Finally, some people count the Anglican Church as Protestant, while others count it as a separate branch.

These differences came about for a variety of reasons. Many reasons were theological in nature, and many were political. Also, many variants succeeded largely because of additional factors: the Protestant Reformation was aided by the printing press and disgruntled German princes, and England's defensible position meant that invasion to depose a reforming king (Henry VIII) was difficult.

AS far as variants and their beliefs, one issue is the existence of denominations. A colloquial definition of "denomination" is "branch of Christianity," but another definition implies that other denominations might be right. I'll focus on the latter. Many Protestants view different Protestants as denominations, but the Catholic and Orthodox Churches each maintain that being "one...[and] catholic" means that other "denominations" are heresies. There's not much bloodshed about that these days, but it does show how some religions view others.

Protestants tend to believe that lay people (non-clergy) have substantial authority in interpreting the Bible, while Catholicism and Orthodoxy tend to spell out every belief and interpretation in the Bible. This is one of the reasons Protestants tend to accept denominations; they're a little more like "let's agree to disagree."

In terms of actual differences, there's a lot, but birth control is a big one. Catholicism teaches that any artificial birth control is always sinful (although it can be the lesser evil in some circumstances), while many Protestants are fine with it. This is also part of the reason for the stereotype of Catholics having many kids. Divorce is similar: Catholics can under no circumstances get divorced (only annulled), while most Protestants accept divorce. It's worldly matters like these that tend to get people more agitated than minor differences in the nature of Christ's holiness.

Jesus was a Jew, but a core belief of Judaism is that the Messiah has not yet come, while all Christians believe the Messiah has come. If you want an analogy, it's more akin to needing new laws and customs to deal with the internet after it came than an "expansion pack."

There is just one Bible, but Protestants leave some books out of the Old Testament that the Catholics include and consider some New Testament books as less important (like James, which explicitly states that works are required for salvation in 2:14-26). The Bible was also assembled over time; it didn't exist for the early years of the church (arguably, the first standardized Bible was the Vulgate in 384).

Paul explicitly condemns divisions in the Church and encourages simply following Christ in 1st Corinthians chapter 1, which is about as close as you get to the Bible talking about denominations.

Such a simple question, and so difficult to provide a simple answer!

Probably the main reasons for Christianity dividing into branches and sects are:

(a) issues of dogma: disagreements about points of doctrine some of which seem with hindsight to be incredibly hair-splitting, such as the precise relationship between Jesus' physical nature as a man and his spiritual nature as son of God

(b) issues of authority: both as regards the authority of people and institutions (does the Pope get the final say?) and as regards the authority of written scripture versus traditional handed-down teaching.

(c) differences in liturgical practice (such as adoration of the saints), sometimes mistakenly thought to represent doctrinal differences.

(d) attempts at reform: reformers like Martin Luther recognising that the church as an institution, or the people running it, had become corrupted and needed to return to first principles.

These days most branches of Christianity are respectful to each other and try to understand each others' point of view; both among theologians and among ordinary followers there is much more acceptance that many of the old doctrinal differences are really technical quibbles of little importance. For example, there is general agreement (and a public statement) that there are no longer any significant doctrinal difference between the Roman Catholic and Anglican traditions. And yet, bringing the two communities back together is extremely difficult, because both are wedded to their traditions and practices, such as the celibate male priesthood in the Catholic tradition; a lot of this is little more than nostalgia, but it is traditions that bind communities together and give them a sense of identity.

The branches come from difference in opinion. Here is a diagram showing where Christianity diverged. Image source

From the beginning Christianity diverged from Judaism¹:

where Christianity emphasizes correct belief (or orthodoxy), focusing on the New Covenant as mediated through Jesus Christ, as recorded in the New Testament. Judaism places emphasis on correct conduct (or orthopraxy), focusing on the Mosaic covenant, as recorded in the Torah and Talmud.²

As time went on further differences in opinion let to more denominations that fell under the umbrella of Christianity.

• Great Schism of 1054 was when Eastern Orthodoxy and Roman Catholicism split over³:

  • issues of the procession of the Holy Spirit
  • whether leavened or unleavened bread should be used in the Eucharist
  • the Bishop of Rome's claim to universal jurisdiction
  • the place of the See of Constantinople in relation to the Pentarchy

• Reformation began around 1517-1521⁴

  • had varying causes and different backgrounds by various leaders (see Martin Luther, John Calvin) caused new denominations to emerge (Lutherism, Calvinism)

• Restorationism attempted to re-establish Christianity in its original form and spans over many years⁵

  • The Second Great Awakening of 1790-1840 was protestant revival movement in America that caused new denominations to emerge (Adventism, Dispensationalism, Latter-Day Saint Movement)

_{This is not meant to be a comprehensive list but a brief summary showing where some denominations OP mentions come from see also}

_{1 https://en.wikipedia.org/wiki/Jewish_Christian#Split_of_early_Christianity_and_Judaism}

_{2 https://en.wikipedia.org/wiki/Christianity_and_Judaism}

_{3 https://en.wikipedia.org/wiki/East%E2%80%93West_Schism}

_{4 https://en.wikipedia.org/wiki/Reformation}

_{5 https://en.wikipedia.org/wiki/Restorationism}