Posted by: chancegill
Halo 3: ODST comes in it's own disc with Campaign, Firefight, and Theater modes. There is a second disc (I consider it free) that holds all of the multiplayer maps and DLC with Halo 3's Matchmaking (No campaign included)
it's not just matchmaking, it's also going to include customs (So you can use the new maps with your friends :D)