OS X Mountain Lion

OS X. It’s what makes a Mac a Mac.

   Built on a rock-solid UNIX foundation, OS X is engineered to take full advantage of the technologies in every new Mac. And to deliver the most intuitive and integrated computer experience.

Multi-Touch, Mac style.
   Use your fingers to tap, scroll, pinch, and swipe your way around the Mac. Because Apple makes both the hardware and software, Multi-Touch gestures are remarkably precise. This precision makes Multi-Touch the most natural and intuitive way to use a computer. When you scroll down on your trackpad or Magic Mouse, your document scrolls down. When you scroll up, your web page scrolls up. When you swipe left, your photos move left. These and many more gestures make all you do on your Mac easier, intuitive, and fun.
Source - http://www.apple.com/osx