This website provides more than the basics of Linux and provides in-depth introduction to the Linux system. It includes easy-to-understand articles in the tutorial as well as a glossary where you can find definitions of particular terms.
This website explains how to manipulate directories and files in the Linux system. For quick tutorial of the following terms such as cd, mkdir, mv, pwd, and rmdir, this website will prove very convenient.
This website offers a more extensive list of the commands of manipulating directories and files as well as changing file access permissions. This website also offers ways to copy, create a symbolic link to a file, etc.