I suggest anyone new to Linux and Unix read this section so that you will jump in with enough knowledge. However, as you get more advanced with Linux you will find manual pages to be an invaluable resource. Use info when looking for Texinfo documentation. Use the command shutdown -h now as root.
Pipes provide a way to get the output of one command into another command.
For instance, if you want to see what's in a very large directory, you can see a screenful at a time by piping the output of ls into less . Redirection is related to the idea of Pipes. This is useful for doing stuff across different systems where you have transferred a file. If the results of md5sum on the same file are different, then the file got corrupted or modified somehow, and you don't want that. You want them to be the same.