Lighting is an option for Graphics3D and related functions that specifies whether to use simulated illumination in three-dimensional pictures.
Lighting -> True uses simulated illumination. The ambient light level is specified by the option AmbientLight. The option LightSources gives the positions and intensities of point light sources.
Lighting -> False uses no simulated illumination. In SurfaceGraphics, polygons are then shaded according to their height, or according to the ColorFunction option that is given.
See The Mathematica Book: Section 1.9.7, Section 1.9.7, Section 2.9.9 and Section 2.9.12.
See also: Shading, ColorFunction, SurfaceColor.