CLI Magic: One-liners
When you are new to Linux you will find that there are more commands to use on the commandline than there are words in the English language (okay not really). But all these choices can be a bit overwhelming. Fortunately, Linux also provides a mean to easily find out what these commands do. These are apropos and whatis.
Linux.com has a quick tutorial showing you how to use both of these utilities to help you on your way to hackerdom.