Well. After 2 pages it seems that no clear answer surfaced.
I did wiki it. But I have too much contradicting information.
Dictionary time:
Monotheism: Belief in only one, usually omnipotent god. Examples: Judaism, Christianity, Islam. (All the same god too.)
Polytheism: The belief in several gods. Examples: Hiduism, The Romans, The Greeks, The Egyptians. (I have no idea what those religious are actually called, but they are polytheistic.)
Atheism: The belief that god/gods does not exist or is not as depicted by other religions. Makes no definition of god/gods. (My personal definition is following science and Occam's razor. So far, it says god does not exist or is not as depicted. For all I know, god may exist. But until I see some hard proof, I'm staying an atheist. Occam's razor will win this one as long as no actual evidence to support god arise, because there's plenty to suggest he doesn't exist. Alternatively, I define him as the Agnostics did. An evil bastard. In my opinion, if god exists, he's fucking evil.)
Agnosticism: The doubt in the existence of god/gods. (Citation needed. I'm not sure about this one either.) Often a stepping stone on the way to atheism but should be considered its own "religion".
Gnosticism: The belief in knowledge. But this whole definition has been disvalued over time. Often thought to be the ancestor to atheism.
Pantheism: I DON'T KNOW!