Linux is an operating system (first syllable pronounced like Charlie Brown's Linus in the UK, pronounced like Lyndon B. Johnson in the US). It is the open source version of proprietary operating systems such as Windows and the MacOS. An operating system allows your computer to run; it sets up an environment in which applications work. No application can work on any computer without an operating system. The operating system is the link between the application and the hardware. Operating systems are also known as 'platforms' or by their initials, OS.