The Blender Internal renderer is only one of the many renderers available to the Blender user. The Cycles renderer has been incorporated into Blender in Blender 2.61, so it's worth looking at. One big difference between the Cycles renderer and the Blender Internal renderer is that you don't need lights in Cycles. Objects can be used as lights. It seems kind of strange, but we will explore it here.
This makes it easy to do cool stuff like neon lights and adding a glow to the bottom of cars. Cycles also handles glass well and creates distortions of light known as caustics, like the light patterns on the bottom of a pool.
Cycles does a style of ray tracing, bouncing the light around and following it to the source. This means that you get better shadows, lights, and reflections. It also means that rendering is never quite finished. It just gets better and better and you decide what is good enough.