O'reillys LinuxDevCenter has made an article/how-to about the absolute power on your Debian system: The root account.
Read about some of the things you can do and the best way to use it right here.
There is one user account on your Debian system that has the power to change anything: the root account. By power, I mean absolute power. The root user account can read, replace, or remove any file. It can read or write to any attached device. It can read or write to any part of the computer's memory. If there's even a mere suspicion that a piece of software is buggy or poses a security risk, there's no way you should run it as root.