The life-style, dentition (teeth), and digestive system of grazers is different from browsers, to handle the problems of eating and digesting grass. This is well illustrated in the evolution of such groups as horses. Ruminants are the largest group of grazers, though many other animals also graze.
When grazers keep eating grass in an area without giving the plants time to grow back, that is called overgrazing.
Grazer Facts for Kids. Kiddle Encyclopedia.