This document provides an introduction to the Linux operating system, including its history and key components. It describes how the GNU Project was established to create a free UNIX-like OS and how Linus Torvalds later developed the first Linux kernel. It outlines some of Linux's main features like being open source and virus-free, and discusses popular desktop distributions like Ubuntu, Fedora and Debian. Certifications for Linux like Red Hat's RHCT and RHCE are also briefly mentioned.