Projector headlights are similar to reflectors in that they both have a bulb that shines in a reflector bowl except that projectors pass the light through a lens before hitting the front of the vehicle.
Reflector headlights do not have a lens. The lens, known as a condenser lens, is used to focus the light. Reflector headlights can have darker spots. Xenon HID bulbs can only be used with projector headlights. HID bulbs are too bright when used in reflector headlights, where the light they emit can blind other drivers.