uhhh.. I get really confused when I play this on the 360 o__O I'm thinking about buying it for the PC, would anyone help me learn it?
Have you ever played a first person shooter on PC before? You might want to get used to using a keyboard and mouse. Seriously I dunno how people manage to use console controllers for FPS games. (unless it's Halo where the game movement is so slow it's easy to hit people)
The idea of the Team Fortress is pretty basic actually, if you're on the red team, shoot the blue guys, and if you're on the blue team, shoot the red guys.
All the while doing that, depending on what the map type is, usually have to capture the control points or if it's 2fort you have to capture the enemy intelligence (like capture the flag).
To do this you have to work as a team (or if you're a rambo style gamer go at it yourself, this sometimes works well if all the other players suck
).
The best thing to do is to watch other people play and do what they do.
The easiest class is to just go as a medic and just heal people lots with your heal gun thingo.
If you have any specific questions, just ask them here. Otherwise it's just a matter of trying things out.