A tilt is a vertical camera movement in which the camera points up or down from a stationary location. For example, if you mount a camera on your shoulder and nod it up and down, you are tilting the camera.
Tilting is less common than panning because that's the way humans work — we look left and right more often than we look up and down.
The tilt should not be confused with the Dutch Tilt which means a deliberately slanted camera angle.
A variation of the tilt is the pedestal shot, in which the whole camera moves up or down.