Ambient Light

An ambient light is actually a point light with the 'Ambient' option set. The point geometry can be used for falloff purposes; for example, you can add a local ambient light source in front of a TV screen to simulate the local illumination it creates, or a local negative ambient light source in a dark corner of a room scene.

Usually ambient light sources work best if the Diffuse option is set and shadows are turned off. Both options are allowed for special effects purposes.