Lens Shift is a feature on select projectors that allows the projected image to be moved vertically and/or horizontally without the need to physically move or angle the projector. Lens shift is an optical adjustment so, unlike digital keystone correction, does not degrade the image quality or resolution. It provides far more flexibility with installation of both the projector and screen.
Lens shift is typically only featured on some mid-high level home theatre and business projectors, it is rarely found on portable or budget models. If your projector does not feature Lens Shift you will need to angle the projector to adjust image position, and rely on the Keystone Correction feature to correct the images’ angle distortion.