The first thing to know about hydronic radiant floor heat is what all those words mean - hydronic refers to the hot water which heats the rooms and radiant is term engineers and physicist coined to describe the type of heat produced. Of course the floor heat bit just means that the heating is kept nicely out of sight under the floor.
So hot water radiant floor heat (less of a mouthful) is a great system for anyone who wants clean lines in their homes, because it is underfloor. More interestingly to most people however, is the fact that this type of heating gives a uniform heat and does not dry the atmosphere so much as blown air heating systems.
Radiant heat flooring that works using hot water needs to run hot water under the floor in pipes. Usually each heated room will have pipes looping forwards and backwards under the floor like a the queue for a really popular Disneyland ride. This way they offer a nice even heat rising from the floor in all parts of the room. The heat is concentrated at floor level which allows most people to lower the thermostat a little.
The water needs to be heated in a home heating boiler (which can be powered by gas, oil, electricity, even wood), then pumped around under the flooring. That is all there is to it!