120hz means smooth playback at 24, 30, 60 fps (3 most common formats), because you can simply show each image for 2, 4, 5 frames. 60hz would mean potentially s

120hz means smooth playback at 24, 30, 60 fps (3 most common formats), because you can simply show each image for 2, 4, 5 frames. 60hz would mean potentially stuttery video at a native 24fps (some movies).