Goblins are mischievous and sometimes even outright evil creatures of legend. They are attributed with various abilities, temperaments, and appearances depending on the story they feature in or what country's mythical history they follow. In some cases, goblins have been classified as constantly annoying little creatures that are somewhat related to brownies and gnomes - and in rare cases even fairies. They're usually depicted as small creatures, ranging from only a few inches tall to about the size of a dwarf. They often are said to possess magical abilities, and tend to be very greedy.
Depictions of Goblins
Lord of the Rings
The author J. R. R. Tolkien generally used the terms of goblin and orc synonymously in The Hobbit and The Lord of the Rings. Smaller orcs tended to be called goblins, but the term occasionally is applied even to large orcs. Tolkien's works, featuring goblins of almost a human stature, generally influenced the depiction of goblins in later works of fiction and fantasy games.
Dark Horse Comics
The Goblins, in this case grotesquely mutated humans, used to live in the underground city left behind by mobsters in the city of Arcadia. When the Crux mob came back they started killing the Goblins and if it wasn't for Ghost and other heroes they would have died. As it turned out, the Goblins lost many people and eventually left the city anyway.
Magic the Gathering
In the Magic the Gathering Universe, goblins are a race of magical creatures. Some possess higher intelligence but most are weak-minded peons and pawns in many Planeswalkers' games.