Mac OS is Apple's desktop and laptop computer operating system, and the software that powers the Mac. Based on BSD UNIX and technologies developed at NeXT, which Apple acquired in 1996, it was first released as a public beta code-named Kodiak in 2001.
OS X Mavericks, was publicly unveiled at WWDC 2013 and released in the fall. The next version, OS X 10.10 Yosemite was shown off at WWDC 2014 on June 2 2014. Next in line — OS X El Capitan — officially arrived on Mac on September 30, 2015.
During WWDC 2016, it was announced that OS X would be rebranded to macOS — keeping the software in line with other Apple products — starting officially with the release of Sierra.