I wish they would have made the whole touch and gesture stuff its own thing and not try to mingle the 2 together, cause then what do you know, playing a game or something you get sticky keys and crap like that.
That appears to be a custom version of the windows + tab screen merged with something like Apple's expose. The windows tab screen normally appears on the left and allows you to switch between modern apps and the desktop.
What you have in the screenshot is not part of the Windows 8 default install.
So it's the trackpad software added a whole expose like feature. I guess that's the only explanation. I did find one guy who reported to have seen the feature, but the shortcut he said worked doesn't work.
It would be nice to use this on my desktop or when using my mouse without having to switch to the trackpad. It also lets you do the same thing when using the modern UI if someone actually uses that.