Volume buttons changing my screen instead of volume?

I recently got a 2013 Macbook Air, but now I'm having a problem. When I press my volume buttons, they don't change my volume, but instead change my screen. If I press the up voulme button, my dashboard slides in from the left. If I press it again, it slides back and I return to the screen I was on. When I press the down volume button, the app/ safari page I have open slide up so I can only see the bottom edge of it at the top of my screen, and a grey translucent border about a half an cm thick pops up around my entire screen. My brightness buttons aren't working either, and sometimes they make the "error" sound (I'm not exactly sure what it's called, just the sound the computer makes when you press a button but it doesn't work). I did the mountain lion update, restarted my laptop twice, but still nothing.

Answers are much appreciated! Thanks (: