Unlike carnivores herbivores like bovines and equines eat only vegetation not even insects and omnivores like chickens and bears eat both flesh and vegetation.
Herbivores are plant eaters they do not eat insects or other animals. They have adapted a head to help them flee from predators. They have large ears that swivel independently. Their eyes are on the side of their head to see behind, on the side and in the front. They have longer legs for running. Their digestive tract starts with a mouth of flat incisors for tearing the plants and molars that can grind grasses and seeds. Their mouths secrete enzymes to digest the vegetation. They have a very large cecum to digest the plant fibers. Their intestines are very long to accommodate the large quantity of food they must eat most of the day.
Bovines have an extensive digestive tract with multiple stomachs and they chew their cud which means that after the first chamber of the stomach does the initial digestion it regurgitates the contents back up to the mouth where the food is chewed mixing it with the enzymes produced in the salivary glands.
Omnivores eat both flesh and vegetation. They have carnivore heads with modified mouth. Their teeth are less jagged than those of the carnivore and contain grinding molars. The mouth excretes digestive enzymes. They have a modified stomach and intestines to digest both flesh and plants.
The Milwaukee County Zoo is an excellent facility to find out about herbivores and omnivores.