macOS is a proprietary, graphical operating system (OS) that powers Apple's Mac computers. It's the primary OS for Apple's Mac computers. macOS comes preloaded on all new Apple Macintosh computers. It's the second most widely used desktop OS, after Microsoft Windows and ahead of Linux. macOS was the first mainstream OS to feature a graphical user interface and mouse input. The macOS desktop interface is called the Finder. It was introduced in 2001 as the successor to the classic Mac OS. The first desktop version, Mac OS X 10.0, was released in March 2001. macOS is designed specifically for the hardware it runs on. It lets you do things you can't with other computers. It comes with a suite of beautifully designed apps.