If you want to be a REAL hacker, you must understand how the system you are hacking works. First you must understand how a login process works. Let's take a look at a fake example. This is a very basic password file.
Every password file has the 'root' account.
Root basically controls the system. Now let's examine what all that stuff means. It might be vice-versa. Now say 'Mr. Hacker' connects to stupid.org and logs in as root.