What is the difference between Reformed and Presbyterian

It's not a dumb question at all. Here's a simple answer that I think may help clarify.
Presbyterian is simply one denomination under one much larger umbrella which is used to categorize a framework or lens for viewing God, the world and scripture. Think of two frameworks like we have mammals and reptiles. These two broad groups are the two main systems of theology - Dispensational and Reformed/Calvinist.

• We can think in broad terms of Christianity having two umbrellas - Catholic and Protestant. [While there are thousands of denominations, they are all basically under one of these two- Catholic or Protestant.] Eastern Orthodox may be an exception, but the priests, and liturgy and church government make it closer to Catholocism.
• So also, it's helpful to think of Protestantism as two large umbrellas - and that 98% of all denominations can be grouped under one of these two camps or umbrellas. Dispensational and Calvinism [Reformed Theology] Reformed Theology or Calvinism is the broader theological framework, or the lens through which they see God and how they interpret scripture.
  Within this broad framework are many denominations of protestant Christianity, and Presbyterian is the largest and most well-known denomination.

Another way of putting this is that Dispensationalism is another lens or system of theology.
Baptist is the largest and most well known denomination which is dispensational.
Most Presbyterians are reformed/ Calvinists, but not all Calvinists are Presbyterian denomination.
In the same way, - most Baptists hold a dispensational view of theology - but not all dispensationalists are Baptist denomination.

There are Reformed Baptists, and independents, and Evangelical Free, and Christians who are Calvinist but not officially part of a denomination.
But Calvinism [Reformed Theology] and Dispensationalism are the two primary systems or lenses, and have very little overlap, so it's not possible to be a Dispensational Calvinist.
Presbyterians or Calvinists have a totally different lens or framework for interpreting end-times, and their entire approach to salvation and eschatology to free will and the role of Israel is entirely different from a Nazarene or Pentecostal, or Church of God.
Dispensationalism refers to the view that there are very specific different time periods in History, and how God interacted with his people in these different dispensations. The most common view is that there are seven different dispensations and now we are in the "Church Age", and most dispensationalists agree that Israel is a real nation, and that it has a unique role in end times events.

In sharp contrast, most Calvinists believe that the Church is Israel, or that the Church replaced Israel, and they would say that many of the passages and promises now apply to the church and Israel and many passages in Daniel and Revelation are viewed as symbolic, and not literal.

Nazarenes, most Pentecostals, most Seventh Day Adventists, most Southern and Free-will Baptists, Holiness, Bible Methodists, United Methodists, Wesleyan, and most Charismatics and most Church of God are Dispensational and therefore, not Calvinist or not Reformed Theology.

that's a totally appropriate question, and certainly shouldn't offend anyone...

here are some resources, which should clear up the understanding that Presbyterians are simply a denomination that teach and align with Reformed church traditions:

The Presbyterian Church (U.S.A.), or PC, is a mainline Protestant Christian denomination in the United States. Part of the Reformed tradition, it is the largest Presbyterian denomination in the U.S., followed by the Presbyterian Church in America. refs

http://www.presbyterianmission.org/ministries/101/

To the point of "reformed church" this is a good description: The Reformation began as an attempt to reform the Roman Catholic Church, by priests who opposed what they perceived as false doctrines and ecclesiastic malpractice—especially the teaching and the sale of indulgences or the abuses thereof, and simony, the selling and buying of clerical offices—that the reformers saw as evidence of the systemic corruption of the Church's Roman hierarchy, which included the Pope.[[2]][2]

If the aforementioned labels seem too specific, but Christian seems too broad, Evangelical Calvinist may be appropriate for those who are Calvinistic, and Reformed (i.e., holding to the Five Solas), but perhaps vary in areas of Polity, Sacramentalism, Eschatology and Cessationism, to name a few. There are many, for example, who espouse Calvinistic theology, Covenant Theology, and Presbyterian polity, but may differ in Baptism, and may not categorically affirm Confessionalism (either Presbyterian, Reformed, or Baptist). They may even differ in views on the Charismata. Yet, the term "Evangelical" (though having developed negative connotations and stereotypes in recent decades) is a legitimate and respectable term which has described Protestant Calvinists (Jonathan Edwards, George Whitefield, John Stott and D. Martyn Lloyd-Jones, most notably) for centuries. While it can also encompass other theological systems (e.g., Revivalism, Arminianism, etc.), "Evangelical" implies the majority of the Protestant movement, and that makes it useful in keeping with broad descriptions; yet, "Calvinist" draws the focus back to the theological framework of the Doctrines of Grace, which unifies Presbyterians, Reformed Churches, Reformed Baptists, certain Anglicans, Congregationalists, and other non-Confessional Calvinistic and Reformed Christians.

Presbyterian is a name that defines a large body of believers. As mentioned above though, there are MANY Presbyterian denominations. As in all large groups, there will be vastly different opinions and beliefs of its members. Some members within a single Presbytery (local group of Pressie churches) will hold to the Westminster Standards (as mentioned helpfully above) and would be considered reformed in their stance. Other members of the same Presbytery might reject the standards of Westminster and thus would not be considered reformed (and I would argue not truly Presbyterian in an historical sense, since they have rejected the standards of Presbyterianism).

So, Not all Presbyterians are reformed (if they disagree with the Westminster Confession as their standard). And certainly there are many, many Christians from other non-Presbyterian denominations who would be reformed and agree with the Synod of Dordt, but do not necessarily hold to the Westminster Confession of Faith as their standard e.g. Reformed Baptists, Dutch Reformed Church. They have other standards such as the 1689 Baptist Confession and the Heidelberg Catechism.

Calvinism would, broadly speaking, be that set of doctrines as taught by John Calvin in his Institutes. These are considered to be a Reformed understanding of Scripture and one of the best Systematic theologies ever written. But whereas the Westminster Confession is ~33 chapters of Systematic Theology, the Institutes are 2 Volumes.

Calvin was in the 1500's on the continent and the WCF was in the 1600's in Britain.

For an excellent summary of Church History and how some of these terms came into being have a look at Sketches from Church History by S.M. Houghton. It is an excellent summary of how the Church developed since the Apostles.