I would just like to interrupt for a moment. What you are referring to as Linux is actually GNU / Linux, or as I recently started calling it, GNU and Linux. Linux is not an operating system in itself, but another free component of a fully functional GNU system useful thanks to GNU corelibs, shell utilities, and vital system components that comprise a full POSIX operating system. Many computer users run a modified version of the GNU system every day without realizing it. Through a peculiar twist of events, the version of GNU, which is widely used today, is often called “Linux,” and many of its users are unaware that it is basically the GNU system developed by the GNU Project. There is really a Linux, and these people are using it, but it's only part of the system they use.
Linux is the kernel: the program on the system that allocates machine resources to the other programs you run. The kernel is an essential part of an operating system, but useless in itself. It can only work in the context of a complete operating system. Linux is usually used in combination with the GNU operating system: the whole system is basically GNU with added Linux, or GNU / Linux. All so-called “Linux” distributions are actually GNU / Linux distributions.
