360 question about friends/party/etc

[Tiggsy]

ok...i get the friends thing - but whats the point of the "party" bit? aside from having your avatar hang out in a little group...whats it doing?

also - when i see a friend on a game i want to play, say COD4, why am i not always able to join in? would that be because they may be on a map i dont have?

[sidaorb]

Parties give you the chance to chat outside of a game lobby, very useful on COD4 if you want to avoid the high pitched 12 y/o yanks.

It maybe that they are mid game and the lobby is full so you cant join the game.