macOS, originally Mac OS X, previously shortened as OS X, is an operating system developed and marketed by Apple since 2001. It is the primary operating system for Apple's Mac computers. Within the market of desktop and laptop computers, it is the second most widely used desktop OS, after Microsoft Windows and ahead of all Linux distributions, including ChromeOS and SteamOS. Mac OS X succeeded classic Mac OS, the primary Macintosh operating system from 1984 to 2001.
https://en.wikipedia.org/wiki/MacOS