When a TV is switched off using the toggle switch on the wall, then there is no electric power consumed by the TV. When the TV is switched off using a remote, then the display on the monitor/screen is off. But a small electronic circuit still is kept powered on to sense the infra red waves from the remote to switch it on again.
So the power is used for communication with the remote unit.
In some TVs with set top box integrated in it or a TV which has more logic and functions other than TV only, the power may be used for other functions too.