Linux is a free and open source UNIX-like operating system. The kernel of the operating system was first released by linus torvalds on October 5th, 1991. After adding user-space applications, it becomes a Linux operating system. Linux is also the most famous example in the development of free software and open source software. As long as you follow the GNU general public license, any individual or organization can freely use all the underlying source code of Linux, and can also freely modify and redistribute it. Most Linux systems also include programs like X Window, which provides a GUI interface. Except for some experts, most people use the Linux distribution directly, instead of choosing each component or setting it themselves.

strictly speaking, the term Linux only means the operating system kernel itself, but it is usually expressed by the Linux kernel. Linux is commonly used to refer to a complete operating system based on Linux kernel, including GUI components and many other utilities. Since these system tools and libraries supporting user space are mainly provided by the GNU project initiated by richard stallman in 1983, the Free Software Foundation proposed to name the combined system GNU/Linux, but Linux does not belong to the GNU project.

Linux was originally a free operating system for personal computers supporting Intel x86 architecture. At present, Linux has been transplanted to more computer hardware platforms, far exceeding any other operating system. Linux can run on servers and other large platforms, such as mainframes and supercomputers. More than 9% of the world's 5 fastest supercomputers run Linux distributions or variants, including the top 1 fastest supercomputers running operating systems based on the Linux kernel. Linux is also widely used in embedded systems, such as Mobile Phone, Tablet computer, Router, TV and video game machine. Android operating system, which is widely used in mobile devices, is built on the Linux kernel.