yea, everything horndude said but some more notes:
typing su in a terminal to get superuser (and not root) access, doesn't mean that outside that terminal you have access to everything. only from within the terminal.
you can also do su root to get root access.
remember also not to experiment around while you have superuser or root access, because unlike windows, one little mistake can happen without notice and next thing you know, Linux is booting up and you don't know what you messed with, so you have to reinstall. more flexibility means more responsibility and care.
have fun with linux!