[Sephiroth]

Difficult to tell, but it looks possible that the RG6 coming out of the splitter feeds another part of your house (it goes up the wall, I think) or another house. Follow it. It's outside grade cable. The brown cables seem to be telephone. The white cable goes into your house.

Again, if you can be arsed, you could feel where the second black cable ( RG6) goes.

EDIT: I read Essjay's assessment after I posted the above.