What are the differences between a man and a machine?

This really depends on how you define machine; some definitions say that Man is a form of machine - for example, you can describe a man as a heat engine. The key difference is the origins; man is evolved and machines are designed and mechanistic. Because of the evolved nature of man, there is enormous parallelism and complexity and an electro-chemical brain. Although complicated machines are designed, the way these are approached is to either start with a simple machine and add complexity gradually, or to break the system into lots of simple machines. There are some system that are being built using artificial evolution and it may be that one day there is a grey area between machines and animals.