Animals are animated living creatures. They reign above plants in the hierarchy and below spiritual phenomena which exists in the air. They have a body and internal organs which act as power centers that relate to parts of their external body.
Animals are creatures of the four elements, they emit heat and smells. Have liquid systems, air systems, are physical in their form and can interact electromagnetically with the world.
The main types of animals are land animals, water animals and air animals. Though you can also categorise them by type like birds, reptiles, insects, bovine, canine, humanoid, etc.
Animals usually either eat other, smaller animals or plants. They seem to live social lives and even play in their own time. Some are domesticated by humans and others form bonds between each other.
Land animals usually have two to four legs in order for them to move around. Some can go into the water or even air but primarily will live above land. Some even dig into the earth and live or hunt there.
They can range in their size and can become quite large but not as large as sea creatures, though usually larger than air creatures. They have dense bones and a lot of muscle, usually. Their skin can be dense too. Some have external fur coats.
Examples of land creatures are deer, lions, elephants, dogs, cats, lizards and humanoids.
Sea creatures are more rounded because they are usually fat dominant and need to have bodies that help them in the water. Deep sea creatures look very strange while other sea creatures can look very beautiful and otherworldly. They can be all kinds of interesting colors.
Physically they are usually defined by having fins, scales and sometimes shells. Their body is not hairy like a land or air animal. It is usually rounded or curvy. They can grow to become incredibly large, more so than land or air animals.
Examples of water creatures are mollusks or shellfish, seabugs like crab and lobster, common fish(tuna, flathead, shark), jellyfish, dolphins and seasnakes.
Animals that inhabit the air usually also live in trees or land onto the earth to hunt and gather. They are capable of flight. Usually they are light and skinny with lots of feathers. They can't fly easily with too much weight so air creatures don't grow too large usually.
They use wings to fly and can either be feathered like a bird or have a shell/plastic like wing as a bug does.
Examples of flying creatures are common birds(owls, crows, seagull) and bugs(moth, mosquito, fly, butterfly).