Linux is the name usually given to any Unix-like computer operating system that uses the Linux kernel. Linux is one of the most prominent examples of free software and open source development: typically all underlying source code can be freely modified, used, and redistributed by anyone.
The name "Linux" comes from the Linux kernel, originally written in 1991 by Linus Torvalds. The system's utilities and libraries usually come from the GNU Operating System, announced in 1983 by Richard Stallman. The GNU contribution is the basis for the alternative (and more correct) name GNU/Linux.