WoW:UI
User Interface
The part of the game mechanincs the player sees and interacts with the game; normally seen through their computer monitor.
In many games, the developers made allowances for enterprising players to craft their own unique look-and-feel for their gamespace. The player can mod just their own client application, or one can upload one's UI mod to one of the many fansites that host file transfers. Players can also download mods by peers and use those UI mods with their client.
By swapping out UI mods, the entire gaming community has the opportunity to find a UI that works for their playstyle.