The primary diet of a herbivore consists mainly of plant materials, including leaves, stems, fruits, seeds, and roots. Herbivores have evolved specialized digestive systems and adaptations to efficiently process cellulose found in plant cell walls. Common examples of herbivores include animals like cows, deer, elephants, and rabbits. Each species may have preferences for specific types of vegetation based on availability and nutritional content. Herbivores play a crucial role in ecosystems, as they help maintain plant populations and serve as a food source for carnivores, thus contributing to the balance of the food chain.