Non-nerd's Guide to Computers/lin
The GNU Project was created by Richard Stallman to develop a Unix-like "free" operating system — software which respects its users freedoms. Unix-like operating systems comprise software collections of applications, libraries, and programmer/developer tools, all overlaid on a "kernel" - the program that allocates resources and communicates with the hardware.
The combination of GNU and Linux is the GNU/Linux operating system, used by millions and usually, incorrectly, simply called “Linux”.
Because of its stability, it is often used on servers and mission critical systems.