FrameXML is the in-house name for the part of Blizzard's standard World of Warcraft User Interface that is implemented in Lua, and hence replaceable by users via AddOns.
Since patch 8.2.0, the FrameXML.toc file no longer includes the interface version.
See also
- Wowpedia:Interface customization
- Category:FrameXML documentation.
- Viewing Blizzard's interface code - to extract all of FrameXML to regular files