This document summarizes the animal kingdom by dividing it into two main groups - vertebrates and invertebrates. Vertebrates have backbones while invertebrates do not. It then describes the key characteristics of major vertebrate groups like mammals, birds, reptiles, amphibians and fish, as well as some invertebrate groups like arthropods and molluscs. For each group, it highlights traits such as how they reproduce, breathe, move, and live in different habitats.