Eels are a kind of fish, though eels have a number of different morphological characteristics. For example, most eels have one continuous fin running along their spine from the typical dorsal fin position on a normal fish to their tail. Most eels have relatively small pectoral fins, if any, and instead primarily locomote via an undulating motion.
Eels, being a varied group of fish, have varied group of abilities. For example, electric eels produce a small incapacitating shock, whereas some species, such as the giant moray eel, have pharyngeal jaws that allow it to more firmly capture prey.
Eels are aquatic, and most waterways can host some form of eel. Electric eels, for example, prefer freshwater lakes and rivers, whereas giant moray eels are more likely to be found off of tropical coasts.