There are a variety of gametypes in Halo 4 and these are generally just ways of categorizing the various games you'll play as each gametype can be further customized to provide incredibly specific rules and styles of play.
For instance, there are games where there are three balls and your team may have to hold all three to score a single point per second (holding two balls gives zero points per second while holding three gets 1 point per second) or a player may score one point for every second they hold any one of the three balls meaning that both teams can potentially score every second. Or, they may simply have one ball and teams have to hold it to gain points. And that ball may or may not explode every so often and reset to a neutral position. OR you may only gain points for kills made while holding the ball... etc.
All of these games, however, would be called Oddball. Because of this, it's difficult to list all the different types of games you might play until the game is released and even then, new gametypes (such as Grifball) are created both by the developers and by players alike and may become part of matchmaking. Until release, we'll cover only the main gametypes and after release, we will try to keep a good list of the minor variations and which playlists they are found in (please feel free to help in this effort).
