What makes the heater work in 2003 Ford Expedition?

I am not sure what you are asking about, but I am pretty sure all heaters work from the heat of the engine. The water flows through and cools the engine off, then is cooled off with the fans in the front (by the grill). The air then flows through this water (the fan doesn't cool it off completely, just a little but below the temperature of the engine. The air then goes through the radiator and into the car. I am pretty sure that is how it works.