This document provides an overview of dinosaurs including: 1) It describes the three periods when dinosaurs existed from 251-65 million years ago and the types of dinosaurs that emerged during each period. 2) It explains that dinosaurs are classified as reptiles and discusses evidence that some may have been warm-blooded. 3) It outlines the three main types of dinosaurs - carnivores, herbivores, and omnivores - and provides examples of each type.