From Halopedia, the Halo wiki
In HaloBall, players must use Golf Clubs to get golf balls into indicated goal areas to score points. As seen in matchmaking, with the default variant of HaloBall players are on teams kept in separate areas, focusing on hammering golf balls up onto a Skee ball style board rather than engaging in direct combat. The number of points awarded depends on which hole the ball eventually falls through.
In the "Xtreme" variant of HaloBall, players must fight through the opposing team to get the neutral set of golf balls through the holes in the sloped board at the other team's end of the playing field.