The Neolithic Revolution is the earliest known Agricultural Revolution. It is very likely that humans practiced forms of agriculture earlier. How much earlier? Well, without evidence, we are guessing. For convenience, anthropologists label humans as hunter-gatherers prior to the Neolithic Revolution. The fact is that the current theory states that agriculture started magically all around the world circa 9,700 BCE. I think it is much more likely this is simply the earliest farming we have yet to discover and will likely push this date back further and further over time.
The Neolithic revolution is the belief in a wide-scale transition of many human cultures during the Neolithic period from a lifestyle of hunting and gathering to one of agriculture and settlement, making an increasingly large population possible. These settled communities permitted humans to observe and experiment with plants, learning how they grew and developed. This new knowledge led to the domestication of plants. A stable lifestyle led to more leisure time and more time to think about things which led to what we would call civilization today. Only the most sturdy of structures from this time period survived the test of time.