Plenty of websites offer valuable information on how to use a command, but you've probably got quite a bit of documentation already on your system. In the following chapters, you'll learn:
How to read and print man pages and info pages. Man and info pages are system documents which can help you understand what many commands are for and how to use them.
How to use the GNOME and KDE help browsers.
Some useful online resources you should bookmark in your browser.
And in Appendix B, you'll find a brief history of Linux -- and Red Hat.