According to Wikipedia:
Sushi (すし, 寿司, 鮨?) is the Japanese preparation and serving of cooked vinegared rice (鮨飯 sushi-meshi) combined with varied ingredients (ネタ neta), chiefly seafood, vegetables, meat (usually fish), and occasionally tropical fruits. Styles of sushi and its presentation vary widely, but the key ingredient in all cases is the rice, also referred to as shari (しゃり) or sumeshi (酢飯).
Sushi can be prepared with either brown or white rice. It is often prepared with raw seafood, but some common varieties of sushi use cooked ingredients, and many other sorts are vegetarian. Sushi is often served with pickled ginger, wasabi, and soy sauce. Daikon radish is popular as a garnish.
Sushi is often confused with sashimi, a related Japanese dish consisted of thinly sliced raw meat or fish and an optional serving of rice.