Absolutely anything you see on your iMac, Mac Laptop, iPhone screen will mirror to your Apple TV 3, onwards. You just have to have the capitability of Airplay on your Mac of either of the above to stream to Apple TV. I know mid 2010 models don't have this option.
You just go to source on the TV and select Apple TV obviously - then flick your Mac to select Apple TV and you're away...
Hope this helps.
