Man Pages are the easiest way to RTFM....

If you have ever been looking for more details than --help or -h provide.  Check for a man page.  Don't know what command to use to make a copy of a file?  Try man -k copy and see what commands come up to help you.  man is the original online help system.  It is one of the most powerful tools to master for new Linux users.  This article gives a brief but helpful intro to man.