I know when I used to play online with my PS2, clans were organized ingame and you could have clan specific matches, and so on. I haven't seen a game on Xbox 360 that does this, but you can have clan tags and stuff like that. My question is...

How are Xbox 360 clans organized, and how do they play against each other? Also if you want to throw in any extra clan info that would be most helpful. Thanks in advance!