How do you play Team Fortress 2 online

Usually when you 1st download TF2(if you havent already)
you are required to download steam.
once you download steam and make a account. open up TF2 and you should be ready.
Also.....you need internet. although you could use bots which dont move or shoot.
The game can only really be played online. If your using a 360 or ps3 you need to have a xbox live account. and your ps3 online