What is the "nature of reality" according to the Buddha?

You are talking about the nature of reality right now

If you really want to know,

You want to experience not reading or knowing.

Readimg and knowing can be a danger without proper guidance.

They can be a hinderance to not being ignorant.

This may be wrong and may possibly not be answering your question completely, but are you maybe refering to "the ten factors" which I have heard described as the "fundamental reality of life".

Additionally, I have heard of delusion being, in essence, the root of suffering. The only problem is that I'm can't quite remember who had said this.

The ten factors go as follows:

Appearance- Nature- Entity- Power- Influence- internal cause- relation- latent effect- manifest effect- consistency from beginning to end-

From this standpoint of logic, ignorence or mis-interpretation (i.e. delusion) of the the ten factors can cause one to not be "in-sync" with the "fundimentql reality of life" which then would lead to suffering.

I hope this helps, and I'm sorry that I havn't been able to give a very good explination or cite who said what very well in this answer, but if you look up "the ten factors" there should be better info. on it.

According to Buddhism, ultimate reality is samsara, endless existence, but it is also impermanent, ever in flux, ever changing. It is empty, yet full. That is, form is always a temporary state of being. Some forms last for millennia, like mountains and oceans, and some are as brief as a lightning bolt. Elements come together to create a particular form, but eventually those elements will break apart again and the object will cease to exist. This is true of everything in the universe.

Source : http://www.patheos.com/Library/Buddhism/Beliefs/Ultimate-Reality-and-Divine-Beings

Can I answer that with some Wikipedia links? I don't know how much detail you want.

The "nature of reality" might refer to the "three marks of existence".

"Ignorance" is said to be the "root" of the "three poisons".

There's a description of ignorance on Access to Insight: which quotes a sutta which defines ignorance (its definition of ignorance is not knowing the "four noble truths"); and which quotes a sutta which explains why it's the cause of suffering (its explanation of the cause is as first of the "twelve nidanas").

Incidentally I was interested to read of the "Four Dharma Seals" recently: they are the three marks, plus nirvana as the fourth. Then there's a note which says, "As suffering is not an inherent aspect of existence sometimes the second seal is omitted to make Three Dharma Seals."

I have read that the Buddha said the cause of suffering is ignorance of the "nature of reality". Is this correct?

Coming into existence or 'birthing' (jati) is the cause of suffering (dukkha). Dependent Arising - Paticca samuppāda by Piya Tan

What is the "nature of reality" that the Buddha talks about?

All conditioned things (forms, verbalization, mental thoughts), are forever changing (anicca), lead to suffering (dukka), and devoid of a permanent entity/owner (anattma). Read about the Tilakkhana or the Three Characteristics in the Dhamma.

may you be happy.

Realities are called Paramattha Dhamma in Buddhism. There are 4 such realities.

1. Citta(consciousness) ex: Vipaaka-citta, Karma, Kiriya-citta.
2. Cetasika(mental concomitants) ex: Vedana, Sanna, Sankhara
3. Rupa(materiality) ex: Patavi, Apo, Tejo, Vayo
4. Nibbana

What is the "nature of reality" that the Buddha talks about?

The first 3 realities listed above have 3 qualitative natures:

1. Anicca(impermanent)
2. Dukkha(unsatisfactory)
3. Anatta(impersonal)

The fourth reality only has the impersonal nature.

The cause for suffering is craving according to the 2nd noble truth. But craving cannot arise without ignorance. It also cannot be uprooted without eliminating ignorance. Ignorance is given as the first link of Paticca Samuppada, the dependent arising process which explains the origins of suffering.

I don't recall any sutta in which the Buddha making that exact statement, but it is inline with Buddhism. It would be more correct if you say "The cause of suffering is craving, which arises due to the ignorance of the nature of reality".