Most animals are multicellular eukaryotes that move, digest food, and reproduce sexually or asexually. They are classified as herbivores, carnivores, or omnivores based on whether they eat plants, animals, or both. Animals have adaptations like fur, horns, camouflage, or behaviors that help them survive and reproduce in their environments. They can also be classified as vertebrates or invertebrates based on whether they do or do not have a backbone.