Rice is a kind of plant, as well as the grain that comes from it. At some Chinese restaurants, you get a choice between white rice and brown rice.
White rice is processed or "polished," so the outer germ is removed — it's a staple of Chinese and Indian cuisine, among others. There are many varieties of rice, defined by the color and length of the individual grain. When rice is a verb, it means "force through a sieve," or in other words, to take something like a potato and make it look like rice. We can trace the origin of rice back to the Sanskrit vrihi-s.