Basically, the idea behind the Paleo lifestyle is that humans have evolved to eat certain foods and move a certain way. These foods include animal proteins, vegetables, fruits, nuts and some animal products. Things like grains, legumes, crop oils, sugars and foods made with them are not part of this diet. This includes all grain-based and processed foods. The Paleo lifestyle is about eating whole foods as close to their natural state as possible. It also includes being active, which is not necessarily the same as exercise! Humans are made to move, not sit in one position for hours at a time. Living the Paleo lifestyle is about living your best and healthiest life!
There are a lot of great resources available to help you learn more about Paleo living. I can personally recommend Paleo Living for Dummies. There is also The Paleo Solution by Robb Wolf and The Paleo Diet by Loren Cordain. Those two books are fairly foundational, but there are many more out there, including cookbooks (even one by America’s Test Kitchen!) There is also Paleo Magazine, which is a great resource for all things Paleo.