I explained this somewhere, but right now I can't remember where. Anyway, the idea is very simple: the generator builds imperfectly symmetrical dungeons. Every dungeon is grown recursively and when a room needs to be expanded, usually identical wings are spawned to the left and to the right from it. Usually, but not every time - occasionally these wings are not identical, but still (imperfectly) symmetrical. How often this happens depends on the desired level of chaos. This all is supposed to produce something in between boring perfectly symmetrical cross-like or T-like plans and too chaotic layouts typical for more common algorithms. That's it.