There are different kinds of "Sushi", depending on the locality. The most common is "Nigiri zushi", originally produced in the Tokyo districet. Nigirizushi consists of small oval-shaped balls of rice seasoned with vinegar and sugar and topped with a thin slice of fish or shellfish, mostly raw but sometimes cooked, or small sliced omelet. Usually horse-radish is spread underneath these slices. They are eaten lightly dipped in soy souce. Slices of pickled ginger may served as a condiment. Other kinds of Sushi are rolls, pressed Sushi, Chirashizushi, Inarizushi, and so forth...