Linux (pronounced LIH-nuks) is an operating system for computers, comparable to Windows or Mac OS X
Linux resembles Unix
you can not only download and run it on your computer, but also download all the source code the programmers created to build the operating system. You can then modify or extend the code to meet your needs.
Linux as having two parts -- a kernel, which is the basic interface between the hardware and other system software,
the functions that run on top of it, such as a graphical user interface (GUI) and application programs.