Animals (or Metazoa) are living creatures with many cells. They are eukaryotes. Animals get energy from other living things. Usually they eat them or are parasites. Some have photosynthetic protists as symbionts.
Most animals are mobile, meaning they can move around. Animals take in oxygen, and give out carbon dioxide. This cellular respiration is part of their metabolism (chemical working). In both these ways they are different from plants. Also, the cells of animals have different cell membranes to other eukaryotes like plants and fungi.