A digital television includes: a display; a tuner; a wireless network interface to transmit data to a mobile terminal and receive audio information and screen; and a controller. The controller is configured to control a signal processor to decode the video signal and the screen information, control the display to display first image corresponding to the decoded video signal with second image corresponding to the decoded screen information, the second image corresponding to an image displayed on the mobile terminal, and receive a command from a remote controller. The controller is also configured to control the signal processor to process the audio signal and the audio information and to output the processed audio signal or the processed audio information to an audio output unit, and to control the signal processor to change the second image's size or position depending on the at least one command received from the remote controller.