The Great Goblin
We don't exactly see the Great Goblin for much time in The Hobbit because he gets killed almost immediately. When the goblins snatch Bilbo and the dwarves from the small cave where they'd been sheltering from a bad storm in the Misty Mountains, Gandalf manages to kill a bunch of the goblins in a flash and then disappear. The goblins bring their captives to the hall of the Great Goblin, who gives "a truly awful howl of rage" (4.30) at the sight of Thorin's sword, Orcrist, which was used by the elves of Gondolin to hunt down goblins back in the day.
When the Great Goblin rushes Thorin with the intent to kill him, all the lights go out in the goblins' hall. Yay, Gandalf is back! Gandalf takes his own elvish sword and stabs right through the Great Goblin in the dark before grabbing the dwarves (and Bilbo) and running for the exit. It's on the pretext of this murder of the Great Goblin that the goblins gather their armies, ally with the evil Wargs (giant wolves), and march against Thorin and his people in the Lonely Mountain at the end of the novel.
Goblins are inherently evil in the world of The Hobbit. They are "cruel, wicked, and bad-hearted." They love making "ingenious devices for killing large numbers of people at once," and "wheels and engines and explosions always delighted them" (4.22). In other words, they like murder and darkness and mechanical things. By contrast, good people such as the hobbits and the elves like songs and nature and artistic things. Tolkien isn't too subtle: the different races of Middle-earth have moral characteristics that seem to be built into their genetic codes. Seem a bit complicated? We get into this a little further in our discussion of the theme on race.
As we mentioned in "In a Nutshell," at least some of the inspiration for these goblins seems to come from Tolkien's reading of George Macdonald's (rather bizarre) novels The Princess and the Goblin and The Princess and Curdie. The one point on which Tolkien totally differs from Macdonald is that Macdonald's goblins have soft, sensitive feet, something that Tolkien "never believed in" (source: The Letters of J.R.R. Tolkien. Edited by Christopher Tolkien and Humphrey Carpenter. New York: Houghton Mifflin, 1981, pg. 178). (Now that's a funny thing to take a stance on.)
But we should also note that there's a change of name between The Hobbit and The Lord of the Rings. The word "orc" appears once in The Hobbit (7.145), while the word "goblin" hardly ever makes it into The Lord of the Rings. They are the same species, but we guess that Tolkien later wanted to distinguish his orcs from the more general goblin tradition. Tolkien traces his own word, orc, from the Old English orc-neas in the poem Beowulf (line 112), which means "ogre" or "hell-devil." For more of Tolkien's unusually anal, careful analyses of his own language use, check out his essay "Nomenclature in The Lord of the Rings."