What are these? What exactly do they do? Skyrim has a bunch of them in the Misc BSA, and all three DLC have them. (Hearthfire only for the cells it affects)

Is this what tells the game where to load grass? My guess is that the CK 'settles' all the grass making sure none of it is floating or clipping, then makes this file, one for each cell. But I can't figure out how to generate them, or if that's really what they do.

Does anyone know more about this? My worldspace is FULL of floating grass that I can't do anything about, so if this is a solution that would be awesome. I've searched the CK and can't find a way to generate them, and nothing seems to open them so I think they're a special filetype just for Skyrim.

What do we know about them?