This document categorizes and describes six different types of animals: mammals, birds, fish, reptiles, amphibians, and invertebrates. It notes that mammals are defined by drinking milk as babies and having hair. Birds are defined by having feathers, wings, tails, and the ability to fly using overlapping feathers. Fish are vertebrates that live in water and have gills, scales and fins. Reptiles are cold-blooded with scaly skin and are born on land. Amphibians are born in water and develop lungs after birth. Invertebrates lack backbones and make up over 95% of all animal species.