Linux is a Unix based operating system. Linux is developed by Linus Torvalds and first version of Linux kernel is released on 5th oct 1991.
Linux was originally developed for Intel x86-based personal computers but now it has been ported to more computer hardware platforms than any other operating system. Linux is used on desktops, server, and in supercomputers. 10 fastest supercomputer runs on some variant of Linux. Linux also runs on embedded systems such as mobile phones, tablet computers, network routers, televisions and video game consoles. The Android system in wide use on mobile devices is built on the Linux kernel.
Linux is a free and open source software. Free means you have not to pay for this Operating system like window. Open source means you are free to used, modified, and distributed source code, commercially or non-commercially by anyone under licenses such as the GNU General Public License.
Linux come with a lot variety of desktop environments:-
5.xfce and many more