Animals are made of many cells. They eat things and digest them inside. Most animals can move. Only animals have brains (though not even all animals do; jellyfish, for example, do not have brains).
Animals are found all over the earth. They dig in the ground, swim in the oceans, and fly in the sky.
Humans are a type of animal. So are dogs, cats, cows, horses, frogs, fish, and so on and on.
Animals can be divided into two main groups, vertebrates and invertebrates. Vertebrates can be further divided into mammals, fish, birds, reptiles, and amphibians. Invertebrates can be divided into arthropods (like insects, spiders, and crabs), mollusks, sponges, several different kinds of worms, jellyfish — and quite a few other subgroups. There are at least thirty kinds of invertebrates, compared to the five kinds of vertebrates.