Originally Posted by L0stS0ul

Rooting is basically becoming super user on the phone. Android is linux at the end of the day and the super user is named "root". Basically the exploits find a way to install a program called SU in the system bin directory on the phone. SU is a program that allows applications or users to temporarily become super user. Once you are super user you can do anything on the phone. Change configuration files, update the OS, change hidden settings, and many more dangerous activities.