Welcome to the world of free and open source software!
Welcome to Linux! GNU/Linux is descended from the UNIX operating system, but it is open source software, which means that you can view its source code and change it to suit your needs. Of course, since this book is geared to those new to Linux, we stay away from very technical issues that are more suited to Linux veterans. This book is going to try to be geared toward the person who has heard about Linux and might be considering trying it out or perhaps the person who has already "taken the plunge" and is looking for more information or wondering where to start now that they have Linux installed. But first, a little history lesson.
The name "Linux" technically refers to an operating system "kernel", a single but key component of a complete operating system. In everyday use, the term "Linux" is frequently used to refer to a complete operating system which consists of the kernel and some of the thousands of other programs required to make an operating system useful. Much of the important system software that is typically installed on a Linux system comes from The GNU Project, a project to build an operating system made entirely of free software.
The first Linux kernel was created by Linus Torvalds. It was first released on 5 Oct 1991. It was started as an x86-only, single-processor operating system, but grew to become one of the most ported pieces of software. Other parts of a complete GNU/Linux system come from other projects such as the GNU project, and are integrated into a complete GNU/Linux OS by your supplier. Usually your supplier will assign their own version number to the integrated whole.
The GNU Project is overseen by the Free Software Foundation, founded by Richard Stallman, who believes that the people should use the term "GNU/Linux" to refer to such an operating system, because so many of the required programs were in fact, written as part of the GNU Project.