Please see the WikiPedia article on the History of UNIX®.
Modern UNIX-like operating systems include Apple Macintosh OSX, Linux, and various "flavors" of BSD deriviatives.
For the average user of a modern UNIX-like operating system, it's mostly a matter of point and click with the mouse within the graphic user interface (or "GUI"), typing on the keyboard, and getting results. But for some users, this isn't enough. They need to experience the power of the command-line interface.