An eel is any fish belonging to the order Anguilliformes, which consists of four suborders, 20 families, 111 genera and about 800 species. Most eels are predators. The term “eel” (originally referring to the European eel) is also used for some other similarly shaped fish, such as electric eels and spiny eels, but these are not members of the Anguilliformes order. (source)