What do animals have in common?

All animals belong to the Animal Kingdom, the Animal kingdom is separated into two parts, there are the animals with backbones, or vertebrates, and animals without, or invertebrates. These groups are split up into smaller groups, for vertebrates, it splits up into Amphibians, Fish, Reptiles, Birds, and Mammals.
For the Invertebrates there are mollusks, Arthropods, and
Sponges.