TORG is a setting where these beings called possibility raiders can attatch their reality to another world (called cosm) and invade it by converting the world to their reality and gaining vast amounts of power in the process.
With the eventual goal of becoming the "TORG" (which is a funny word for godlike being)
The basic setting in this case is that Earth has been invaded by several other cosms, each with it's own "genre" (horror, sci-fi, lost worlds, fantasy, etc) And the players goal is to defend the world from these invaders and their minions.