Pyramid charts are very similar to pie charts and can be mostly used for the same purpose. But there is one more piece of information that can be given by using pyramid charts, a sense of hierarchy. The pyramid has a top and bottom layer and there are layers in between too, usually the top layer being the most important.
Look at the project files in the code folder. Also, having a good grasp on the Pythagorean theorem, available at http://en.wikipedia.org/wiki/Pythagorean_theorem, is important.
The following are the steps required to create a pyramid chart: