The Blender Internal renderer is only one of the many renderers available to the Blender user. The Cycles renderer has been incorporated into Blender 2.7, and development has stopped for the Blender Internal renderer. The Internal renderer is good and easy to use so it's a great way to start. However, in the long run, you will need to know the Cycles renderer.

One big difference between the Cycles renderer and the Blender Internal renderer is that Cycles simulates real light while the internal renderer does not, so Cycles gives you better results. The Cycles renderer also allows objects to be used as lights.

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 swimming pool.

Cycles does a style of ray tracing, bouncing the light around and following it to the source. This means that you get better...