Mac OS is an operating system like Windows and Linux desingned for Mac computers that was released in January 24, 1984 by Apple, although more expensive than the regular Microsoft Windows. Today, Apple's Mac is still more expensive than Microsoft Windows.
The current version is Mac OS X Mojave 10.14.1.
The Macintosh OS originated on the first Apple Computer, the Apple Macintosh. It preforms the same functions as Windows but doesn't has a library as vast as Windows and is therefore best suited for business and school use. It doesn't have many games for its platform but is desired for certain programs like GarageBand, a music editing software, and iMovies, a movie maker. The Macintosh OS was named after Steve Jobs' favorite type of Apple, the McIntosh Apple.
Mac OS has a tool called Boot Camp Assistant that allows the user to install Windows on a Mac OS, this is due to how Apple originally designed the Personal Computer on MS-DOS, which in the final versions of Macintosh, was changed entirely, making it a standalone Personal Computer.
Only a few pieces of malware are targeted towards Macs, due to the lower market share, and the fact that it is harder to write programs for.