Mac OS X 10.7 Lion is the eight major release of Mac OS X operating system
Mac OS X Lion is the eighth major release of Mac OS X, and the seventh major upgrade to the OS since Mac OS X 10.0.
It was released on Wednesday July 20th 2011 via the Mac App Store for $29.99/£20.99. As of July 25th, 2012, Mac OS X Lion is no longer available on the App Store, and was replaced by its successor, mountain-lion.
Major upgrades include various iOS inspired interface changes such as Launchpad, an app launcher; the transition from Expose to Mission Control; new multi-touch gestures; integrated Auto Save and Versions, which allows users to manage versions of saved files. The first developer preview was released on February 24, 2011 with a second version being released at the 2011 World Wide Developers Conference.
System Requirements for OS X Lion: