Linux distribution (often called a distro for short) is an operating system made as a software collection based on the Linux kernel and, often, on a package management system. Linux users usually obtain their operating system by downloading one of the Linux distributions, which are available for a wide variety of systems ranging from embedded devices (for example, OpenWrt) and personal computers to powerful supercomputers (for example, Rocks Cluster Distribution).
A typical Linux distribution comprises a Linux kernel, GNU tools and libraries, additional software, documentation, a window system (the most common being the X Window System), a window manager, and a desktop environment. Most of the included software is free and open-source software made available both as compiled binaries and in source code form, allowing modifications to the original software. Usually, Linux distributions optionally include some proprietary software that may not be available in source code form, such as binary blobs required for some device drivers. Almost all Linux distributions are Unix-like; the most notable exception is Android, which does not include a command-line interface and programs made for typical Linux distributions