I found this site discussing the difference between copyright, trademarks, and patents. I found it interesting because each of these things are much different that I had originally thought them to be. I also found it funny that patents do not last as long as do copyrights. If you ask me, I think that patents should last longer because I feel that inventing something is the most solid, original idea that can be produced.
With patents it kind of makes sense because it gives the inventor enough time to really establish a business around their invention, but not too much time that a corrupt sort of monopoly could be established.
I think Claire is right with the patents overall main purpose. It protects the inventor but also protects the buyers, which is important when starting a business.