Linux is a free, open-source software operating system (OS) built on the Linux kernel. It was created by Linus Torvalds after he became curious about operating systems while attending the University of Helsinki in 1991. When he ran into licensing issues, he began work on his own OS kernel, which ended up as the Linux kernel. He made the source code freely available under the GNU General Public License. This spawned a rich diversity of Linux distributions (distros) built around the same Linux kernel.
Originally intended for personal computers, Linux has been ported to more platforms than any other OS. Linux is found on Android smartphones and is the leading OS on servers and mainframe computers. In late 2017 it eliminated the last of its competitors to become the only OS used on the TOP500 supercomputers. It is also found in many embedded systems, including DVR devices, routers, televisions, smartwatches, video game components and even the screens you watch on airplanes. It is used by some of the world’s most demanding computing environments, including the New York Stock Exchange, Google, Amazon, and the U.S. Postal Service.
A Linux distro includes the Linux kernel, a variety of utilities and libraries which are typically provided by the GNU Project, and the application-related software that supplies the functionality offered by the distro. There are hundreds of free Linux distros, including popular players like CentOS, Debian, openSUSE, Linux Mint, Fedora, and Ubuntu. Commercial distros such as SUSE Linux Enterprise Server are built with enterprise-quality testing and hardening, which creates very stable, supportable versions that can be used even in organizations that are governed by exacting regulatory standards. According to IDC, organizations of every size are now using Linux for business-critical workloads, due to such capabilities as geo clustering, live patching, and full system rollbacks.