[youtube]http://www.youtube.com/watch?v=XMf4Fx4UTRU[/youtube]
powernap is a new feature of OS X Mountain Lion that was specially designed to allow users to keep their Macs up to date with all Apple applications/services when theoretically they should be in sleep mode. The function will be available on MacBook Airs and MacBook Pros with Retina Display, but for now Apple has released a firmware update that brings the functionality only to Airs released last year and this year. After performing that update you will have a menu for PowerNap in System Preferences.
You can download PowerNap from here:
Here you find all the necessary information about the PowerNap functionality.
