A Linux distribution, often shortened to Linux distro, is an operating system compiled from components developed by various open source projects and programmers. Each distribution includes the Linux kernel (the foundation of the operating system), the GNU shell utilities (the terminal interface and commands), the X server (for a graphical desktop), the desktop environment, a package management system, an installer and other services. Many components are developed independently from each other and are distributed in source code form. Distros also include an Internet browser, management tools and other software such as the KVM hypervisor. A single Linux distribution may contain thousands of software packages, utilities and applications.
Linux distributions compile code from open source projects and combine it into a single operating system that can be installed and booted up. Linux distributions are available for desktop computers, for servers without a graphical interface, for super computers, for mobile devices, and for special uses, such as home theater PCs and embedded systems. Because it is open source software, anyone can make their own Linux distribution by assembling it from the source code themselves, or by modifying an existing distribution. Currently, more than 300 Linux distributions are actively maintained.
There are commercially backed distributions, such as Fedora (Red Hat), openSUSE (SUSE) and Ubuntu (Canonical Ltd.), and entirely community-driven distributions, such as Debian, Slackware, Gentoo and Arch Linux. Most distributions come ready to use and pre-compiled for a specific instruction set, while some distributions are distributed mostly in source code form and compiled locally during installation. Some commercial distributions charge users a fee for support and customer development services. Open source licensing prohibits charging for open source software.