Complex sentence: Sushi refers to any dish made with vinegared rice; and, while raw fish is one traditional sushi ingredient, many sushi dishes contain seafood that has been cooked, and others have no seafood at all.
Split into simpler sentences: Sushi refers to any dish made with vinegared rice. While raw fish is one traditional sushi ingredient, many sushi dishes contain seafood that has been cooked, and others have no seafood at all.