Herbivores are animals that eat plants. They are herbivorous animals.
People who eat mostly plants are usually called vegetarians, rather than herbivores.
Herbivores (such as deer, elephants, horses) have teeth that are adapted to grind vegetable tissue. Many animals that eat fruit and leaves sometimes eat other parts of plants, for example roots and seeds. Usually, such animals cannot chew or digest meat. But some herbivorous animals will eat eggs and occasionally other animal protein.