A method of controlling a display device, and which includes obtaining, via camera of the display device, a user's image; recognizing, via a controller of the display device, a user's hand gesture from the obtained user's image; and when the recognized user's hand gesture does not match a pre-stored gesture, displaying, via a display of the display device, a function guide including different hand gestures different than the recognized user's hand gesture for guiding a user's selection for performing a function of the display device.