This is a little clip that covers the camera on your iMac when you don't want to be spied upon. The microphone is not obstructed. It clips on easily and can easily be removed or just slid to the side. The cover fits generation 6 iMac (mid 2011 edition) machines.
The idea behind it is that if you like to work with your underwear wrapped around your head at home like I do most of the time... and don't want some ratters to record a video of that and post it on YouTube, then you'd be on the safe side with this covering the lens of your webcam. Because let's be honest. When you are concentrating on your screen, would you really notice the light of your webcam come on?