Lighting is a very important topic in rendering, standing equal to modeling, materials and textures.
The most accurately modeled and textured scene will yield poor results without a proper lighting scheme, while a simple model can become very realistic if skillfully lit.
Lighting, sadly, is often overlooked by the inexperienced artist who commonly believes that, since real world scenes are often lit by a single light (a lamp, the sun, etc.) a single light would also do in computer graphics.
This is false because in the real world even if a single light source is present, the light shed by such a source bounces off objects and is re-irradiated all over the scene making shadows soft and shadowed regions not pitch black, but partially lit.
The physics of light bouncing is simulated by Ray Tracing renderers and can be simulated within Blender by resorting to the Radiosity (the chapter called Radiosity (x)) engine.
Ray tracing and radiosity are slow processes. Blender can perform much faster rendering with its internal scanline renderer. A very good scanline renderer indeed. This kind of rendering engine is much faster since it does not try to simulate the real behavior of light, assuming many simplifying hypothesis.
In this chapter we will analyze the different type of lights in Blender and their behavior, we will analyze their strong and weak points, ending with describing a basic 'realistic' lighting scheme, known as the three point light method, as well as more advanced, realistic but, of course, CPU intensive, lighting schemes.