Can you explain the Haber-Bosch nitrogen fixing process?

I came across a book in a bookstore that gives a history of the people who developed the process. I understand that the net result is to break up nitrogen molecules so that the nitrogen atoms can be used for things like the production of fertilizers. (I was always under the impression that petroleum was used to make commercial fertilizer.) The book claims that the development of the Haber-Bosch process is one of the most significant developments of recent times.

What I would like is an overview of what is happening from a chemical point of view. I did a Web search on this and I am still not sure what is going on. I think the process may produce ammonia, but I am not sure. There was also something about the signficance of the use of catalysts.