Lion is another name for Mac OS X 10.7, the eighth version of Apple's desktop operating system. It was released on July 20, 2011, almost two years after Mac OS X 10.6 Snow Leopard and preceded the release of Mac OS X 10.8 Mountain Lion. Lion was the first version of Mac OS X to be released on the Mac App Store and was not sold on a DVD like previous versions of the operating system.
Mac OS X 10.7 Lion was one of the most substantial updates to Mac OS X and included more than 250 new features. Most notably, Lion added several features from iOS, Apple's mobile operating system that runs on the iPhone and iPad. For example, Lion supported several new multi-touch gestures, such as swiping to switch between applications and to navigate between webpages. Additionally, the user interface was updated to look more like the iOS, with hidden scroll bars and a bouncing animation when you scroll past the top or bottom of a page.
In an effort to make Mac OS X 10.7 more like iOS, Apple also introduced system-wide support for full-screen apps, which hides the menu bar and allows the current application to fill the entire screen. Several of Apple's own applications including Safari, Mail, iPhoto, and Pages, were updated with full-screen support when Lion was released and many third party applications were updated shortly after. Lion also introduced "Launchpad" (similar to the Launcher included with early versions of the Mac OS), which provides one-click access to all programs installed in the Applications folder. Finally, Lion added a "Resume" feature that saves the state of open windows in applications, so they reappear automatically when you reopen a program or restart your computer.
The last Lion software update was 10.7.5, released on October 4, 2012.