EDIT: antime already awnsered to the question that was here.
Ever seen a SNES game with a curtain effect, like the Super Mario World opening (the cartoon-style "ball" fade-in)? It's a setting that "clips" a BG to a given size. Saturn has the mother of all clippers... SNES had horizontal clippers only to a given color. Saturn can do clipping on the horizontal and vertical locations, and show the inside, the outside, overimpose two windows with AND (a way to create transparency without cost) and er... lots of other fancy stuff.
To add to that, you had to make a special DMA mode in SNES to let the window do fancy drawings, that had some processor cost. VDP2 eats stuff like that for breakfast
It's very exciting stuff ^^;;;