Mountain Lion is another name for Mac OS X 10.8, the ninth version of Apple's desktop operating system. It was released on July 25, 2012, almost exactly one year after Mac OS X 10.7 Lion. Like Snow Leopard, Mountain Lion was not a major update to the Mac OS. Instead, it was primarily a performance update and included a small number of enhancements to further integrate Mac OS X with iOS, Apple's mobile operating system.
Unlike previous versions of Mac OS X, Apple officially labeled Mountain Lion "OS X" (removing "Mac" from the name). This change, while symbolic, represents Apple's effort to integrate their desktop computers and mobile devices into a more cohesive environment. For example, Mountain Lion allows Macs to share reminders, notes, and documents with iOS devices using the cloud. Notification Center, introduced with OS X 10.8, provides many of the same updates as the Notifications feature in iOS. The new Messages application can send and receive iMessages, which allows Mac users to communicate directly with people using iPhones and iPads.
OS X Mountain Lion also added a few other notable features. including Dictation, which converts speech to text, and AirPlay, which streams media to other Apple devices. OS 10.8 also includes Gatekeeper, a tool that protects your Mac from malicious software. The new Power Nap feature updates Mail, Contacts, Calendar, and Reminders data, on Mac laptops while they are in sleep mode. Additionally, Mountain Lion includes several new social networking features, such as a "Share" button added to applications, Facebook and Twitter integration, and Game Center, a social gaming network that was previously only available on iOS devices.
NOTE: Like Lion, Apple's Mountain Lion operating system is not sold on a disc, but is only available as a download from the Mac App Store.