The document categorizes animals into different groups including mammals, reptiles, amphibians, fish, birds and insects. It provides defining characteristics for each group: mammals give birth to babies and feed them milk; reptiles are cold-blooded and have scales; amphibians can live on land and in water; fish have tails, fins, gills and scales and live in water; birds have feathers, wings and lay eggs, most can fly; insects have six legs and wings and a three-part body. It also suggests additional ways animals can be classified such as whether they are diurnal or nocturnal, whether they have a spine or not, and whether they are herbivorous or carnivorous.