The World of Warcraft game client provides many functions available for use in Lua script files provided by AddOns. These functions are the WoW API, are also used by Blizzard to build the game client interface. They allow addons to query information about the player and the game world, to receive notifications (events) when the player interacts with the game world, and to trigger player actions like changing target, casting spells, using professions, using vehicles, joining a group, etc.