Holy smokes, that's the coolest thing I've found out about recently. I'm trying to wrap my head around where this sits within the OS. Is it a layer "on top" of

Holy smokes, that's the coolest thing I've found out about recently. I'm trying to wrap my head around where this sits within the OS. Is it a layer "on top" of everything? Or does it sit "underneath" the higher level os functionality? Apologies if that doesn't make any sense, it looks to be a really cool tool and I'll be investigating it regardless.