Events are a basic and important message passing system for WoW and its UI. The Event API and the WoW UI are built around these messages being recieved by Frames from WoW, through the use of event handlers, and by expressly registering for messages for a frame. An OnLoad event fires for a Frame during load, allowing it register for these event messages. The List of all Events details this event API by providing a reference for each of these messages.