There are quite a few species. All have an annulated appearance and look more like giant earthworms than anything; they also have (usually small) eyes and a pair of characteristic tentacles emerging from pits on the face. They are circumtropical. IIRC, the aquatic varieties are illegal in the US but the terrestrial/fossorial ones are still permitted.
Had one a while back. Pretty interesting little guy. I kept mine in a full aquatic setup. Do a search for caecilian worm or rubber eel to find some more info.
THey're easy to keep, I had a trio I sold a few years back, they ate bloodworms, blackworms, and pellets. I kept them in a 10g planted tank. Never had any issues..