These small creatures are found in many stories. Most often portrayed as evil imp-like creatures that delight in playing tricks on humans. In role playing games they are a tribe of demi-humans that are often found in wilderness areas that attack travelers.
The numerous ugly, dumb, short creatures ruled by Jareth. Presumably most or all of them were turned into goblins from babies offered to him.
In the Harry Potter universe, goblins are small creatures that run Gringotts bank. Very little is known about goblins in general, but they are described as having clever faces and long fingers and feet. Goblins seem to be very greedy, and Hagrid commented that with goblins running Gringotts, a person would have to be mad to try to rob them.