Linux (i/ˈlɪnəks/ lin-əks or /ˈlɪnʊks/ lin-uuks) is a kernel assembled under the model of free and open source software development and distribution. It was first released 5 October 1991 by Linus Torvalds.
Linux is usually installed in a computer using a GNU/Linux distribution (distro), whereof the most common are, as of december 2013 Mint GNU/Linux, Debian GNU/Linux, Ubuntu GNU/Linux, Mageia GNU/Linux, Fedora GNU/Linux and openSUSE GNU/Linux.
Most of the time people mistake the kernel for a whole operating system, however that is simply not true, what most of the people refer to as "the Linux operating system" is actually the GNU Operating system combined with the Linux kernel, because of that it's called GNU/Linux or GNU+Linux
Origins and development
Linus Torvalds originally developed Linux as a free operating system for Intel x86-based personal computers. Linus proposed the name Freax, but the sudden storm of interested helpers ignored the proposal and instead termed it Linux.
The development of Linux is one of the most prominent examples of free and open source software collaboration: the underlying source code may be used, modified, and distributed—commercially or non-commercially—by anyone under licenses such as the GNU General Public License. Typically Linux is packaged in a format known as a Linux distribution for desktop and server use. Some popular mainstream Linux distributions include Debian (and its derivatives such as Ubuntu), Fedora and openSUSE. Linux distributions include the Linux kernel, supporting utilities and libraries and usually a large amount of application software to fulfill the distribution's intended use.
It is a leading operating system kernel on servers and other big iron systems such as mainframe computers and supercomputers: more than 90% of today's 500 fastest supercomputers run some variant of GNU/Linux, including the 10 fastest. Linux also runs on embedded systems (devices where the operating system is typically built into the firmware and highly tailored to the system) 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.
A distribution oriented toward desktop use will typically include the X Window System and an accompanying desktop environment such as GNOME or KDE Plasma. Some such distributions may include a less resource intensive desktop such as LXDE or Xfce for user with demands for a more classic user interface.
A distribution intended to run as a server may omit all graphical environments from the standard install and instead include other software such as the Apache HTTP Server and an SSH server such as OpenSSH. Because Linux is freely redistributable, anyone may create a distribution for any intended use. Applications commonly used with desktop GNU/Linux systems include the Mozilla Firefox web browser, the LibreOffice office application suite, and the GIMP image editor.