The term "Linux" refers to a family of operating systems based around the Linux kernel. These grew out of an attempt to produce an open source version of the operating system Unix during the 1980s. Linux is used as the operating system for most of the world's servers and forms the basis of Google's popular mobile OS, Android.
Between 1971 and 1983 AT&T, the owners of Unix, were forced by an historic antitrust ruling to license the source code of their operating system to anyone who asked for it. This led to Unix becoming popular among academic users as they were able to easily alter the OS to suit their needs. With the antitrust ruling ceasing to be applicable in 1983, AT&T promptly commercialised Unix, which led immediately to the setting up of the GNU project, an attempt to create an open source Unix-like system.
With no kernel for GNU available by the start of the 1990s, programmer Linus Torvalds stepped in and created his own Linux kernel for use with the GNU software. Torvalds still oversees the development of the Linux kernel which has now been ported to more hardware platforms than any other operating system.
Popular Linux distributions include Debian, Fedora and OpenSUSE. There are also commercial derivatives of these such as Red Hat Enterprise Linux, based on Fedora, and SUSE Linux Enterprise Server, based on OpenSUSE. A variety of user interfaces can be used with Linux ranging from sophisticated graphical interfaces like GNOME to simple text interfaces.