I think it is important to mention that he first started out as a Dutch doll that one of Tolkien's children owned;
Tolkien first wrote about him in "The Adventures of Tom Bombadil" long before he introduced him into the Lord of the Rings trilogy,not much different was done with him but the peacock feather in his hat was changed,since there where no peacocks living in Middle-Earth(you can read Tolkien,Letters,pp.318 to 319 to learn more about that). I'm not quite sure what exactly Tom is but in the chapter "Council of Elrond" it seems he is a nature spirit,but it does not directly say so, "Power to defy our Enemy is not in him, unless such power is in the earth itself" and ". . . now he is withdrawn into a little land, within bounds that he has set, though none can see them, waiting for a change of days, and he will not step beyond them" Rings, 1:279).
I hope you find some of the info helpful but I don't know very much about Tom Goodluck on your essay!

[Edited on 3/11/2003 by LadyFeawen]

Ya know, I can never pronounce Tom Bombadil's name in real life. Usualy I just get fed up of trying and end up nameing him Tom Bomdidly or worse yet; TOM BIDLYBIDLY!
Anyways, I found a site that might help you with your essay, so I posted the url below.
http://tolkien.slimy.com/essays/Bombadil.html
Hopefuly you haven't done your essay yet, or boy am I gonna be red faced!