User blog comment:Jkphantom9/RWBY Livestream Recap/@comment-2135507-20140822011904/@comment-24435688-20140822015157

My understanding of it all is that Vale, Atlas, and Vacuo are kingdoms with Vytal, Mantle, and Mystral being continents (or regions if you prefer).

Mystral may or not be the name of the fourth kingdom and share that name with the region it is in.

This is what I've gotten from the RWBY crew's attempted explanations.