FrameXML is Blizzard's in-house name for the part of the standard World of Warcraft User Interface facility that allows UI contrstucts and Frames to be implemented using XML templates, and hence replaceable by users via AddOns.
There is a fairly good bit of difference between Blizzards FrameXML facility, and whatever Blizzard implemented in "FrameXML". The latter, from our perspective, are really just another set of APIs and Objects developers are presented with. Similarly, there is also a difference between the base WoW Lua API that comes from the base game (not defined in any visible FrameXML), and the Lua language and Blizzard WoW extensions to that. To disambiguate the differences, there are three (or four) major categorites of 'UI Customization' documentation on WoWWIki.
Starting at the highest level:
- XML UI - This documents the actual FrameXML facility, both for those that want to use FrameXML as a part of their AddOns, and for critical understanding of the Widget API, since practically all of the Blizzard "Widget" code uses the FrameXML convention.
- Widget API - The crossroads of UIOBJECT Layout and Event API, and Blizzard Widget Lua-side API documentation. This one actually covers the most ground, but all-together can be thought of as all of the pre-defined UI objects and APIs found in Blizzards FrameXML.
- WoW API - The core Blizzard WoW API exposed to Lua code.
- WoW Lua - The WoW customized flavor of Lua.
- XML UI
- WoWWiki:Interface customization
- Category:FrameXML documentation.
- Viewing Blizzard's interface code - to extract all of FrameXML to regular files