Game Updates.....

You kno when u start up a game, you already connected to XBOX Live. As soon as you start up on some games it'll say there is an update for. so it installs the updates, and restarts. My question is what updates are they puttin on da the game/system? I try playing the game to see if any thing is different but i dont know whats new. I know its not updates for new multiplayer maps because I would of seen those plus you have to go to XBOX Live Marketplace while playin da game to get those. So what updates are they puttin on da game/system? Say FEAR %26 The Darkness, those were games that had updates for them. could anyone also tell me the updates for those games if they know?Game Updates.....
Sometimes it may be small glitches found later in the game, or fixing bugs, etc that interfere with the game. It can be anything basically most of the time you won't even notice what was fixed.