Rooting is the process of attaining privileged control (known as "root access") on a UNIX based device. A rooted device is one on which root access has been gained.
A rooted device is one on which root access has been gained.
On android rooted devices are popular to allow additional things to be achieved, such as accessing all files for backup purposes.
On iOS devices, making a device into a rooted devices is given the term jailbreak.