Some Info for you Kevin:
http://en.wikipedia.org/wiki/Grand_Theft_Auto_IV#Multiplayer

Also:
"Multiplayer mode is accessed by pulling up your phone, choosing multiplayer, then choosing either a ranked or player (non-ranked) match. From there, you can pick the game type (they each have the same game types, except player match has the free roam option, which disables objectives and teams). You can also organize your friends into a party, in which you can mess around in free roam until the party leader chooses the game to join. (You'll return here between games as well.) "

The official site:
http://www.rockstargames.com/IV/#?page=multiplayer