Can someone explain to me WTF is the Steam Machine controller?

[Mythmaker1]

richardhutnik said:

Mythmaker1 said:

The picture didn't really show the back, but the page linked in the OP has more detailed schematics. The buttons I'm talking about are...

Can't tell by that diagram if those are buttons or a Vita type sensor area.  A sensor area is different than buttons.

The press release says that they're buttons. Also, if you look at the photo they released, you can see it peeking out at the bottom.