This tutorial, hosted by The Linux Documentation Project (TLDP), covers most of the basics needed to understand and use the Linux operating system (OS). A derivative of UNIX, Linux is a popular OS used in many technical applications. Thus, it is probably not intended for home users. It is mostly text-based, but there are some screenshots and figures of various tools. The author does a good job explaining key concepts, such as redirection, manipulating files, and command line arguments. Many other guides and resources can be found on the TLDP hom page.