So... Huh, since I'm new to College Football, could someone explain me how the divisions work ? I'm kinda lost.
Not sure what exactly what level of detail you're wanting, so I'll just go from the top down.
Virtually all discussion here is about NCAA Football Bowl Subdivision (FBS, formerly known as 1-A). The champion here is determined by a 1-game playoff between the two highest ranked teams, as determined by a combination of human polls and computer-generated rankings. After that one game, there's like 35 bowl games, which are kinda glorified exhibition games.
The biggest of the bowl games are the Bowl Championship Series (BCS) games, which are the Orange, Sugar, Fiesta, Rose Bowls, and the BCS National Championship game.
So moving more toward divisions for you: Included in NCAA FBS are 11(?) conferences, which is the basic organizational unit, and a handful of Independent teams. Of those conferences, 6 are designated as BCS Automatic Qualifiers, which means that the champion of those conferences get automatically invited to one of those BCS games I mentioned, while any other team from any conference can be invited as one of the 4 BCS at-large teams should they meet a certain criteria.
And for divisions specifically: Some of those 11 conferences have too many teams to play a round robin during the season, so they split into 2 divisions. In these conferences, the two teams that win their division go on to meet in the conference championship game. The winner of that game is considered the conference champion.
Edit: That's probably
way more than you wanted, heh.