In Japanese cuisine, unagi is freshwater eel. If you order unagi sushi, you'll get a piece of barbecued eel on sticky rice.
Unagi is commonly found on menus in Japanese restaurants, and unlike many dishes that include raw fish, it's always fully cooked. Raw eel is actually poisonous, whether it's freshwater (like unagi) or saltwater (which is called anago). While unagi is an extremely popular type of sushi, it's considered to be an endangered species in Japan.