Ambient Light is designed to splay light in all directions and is usually good for close to ceiling applications.
Down Lighting directs light downwards by using open bottom shades to minimize the amount of light that is projected upwards towards the ceiling.
Up / Down Lighting
Up / Down Lighting or convertible bathroom fixtures are designed to be mounted either way. Although some fixtures may only be pictured in one direction, these fixtures will have specialized shade mounting hardware to eliminate the possibility of the shade detaching from the fixture as well as compensate for heat displacement when mounted downward.
Up Lighting is classically the most common form of bathroom lighting and although the light is being directed upwards will still provide ample illumination for many applications.