You can learn basic Linux and UNIX commands in the following tutoriel : http://www.ee.surrey.ac.uk/Teaching/Unix/

Manual Pages. in UNIX systems the “man” command allow you to obtain information about commands, you only need to type (“man ls” for example this will load the manual for the ls command). You can also search the manual by typing : “man -k keyword”, if you need to look for random commands for example you only have to type “man -k random”.