What is the software to move screen/laptop to apple TV screen I have seen users that drag their screen to AppleTV on WiFi for presentations and such. I want to be able to do this but can't find the software. I ask and they say it is built in.

I have MacBook Pro with OS X 10.7.5 I have the most recent updates. Is this software available?
This is called AirPlay Mirroring.
How to use it on a second generation Apple TV or higher can be found on Apple's site here and here