Wikipedia has done a decent job of describing the system.
After looking at wikipedia I remembered the one great benefit that I have in my own system is that I have run copper pipes through my wood stove so the wood stove does all the work with a kerosene boiler as a back-up. It is very efficient.
I am not sure how this site works but I could give you a lot more detail through e-mail. But, I am not interested in displaying my e-mail address on the site. If you know a way to "request" an e-mail address via this site, I'm game.