Simply put, a geothermal heat pump takes heat energy and efficiently moves it to suit your need.
Geothermal. Ground Source Heat Pump. Geo unit. Heat with dirt. It is all saying the same thing.
You are heating and cooling your home by transferring the heat to and from the earth.
IN THE WINTER, the geo unit takes the heat energy from the Earth and transfers it into your home. Whether you have radiant floor heat or forced air, you will be comfortable and warm.
IN THE SUMMER, with a clever reversing valve, the geo unit takes all that heat that you are trying to get rid of on a sweltering day and puts in into the cool 50 degree Earth, where direct contact---conduction---allows the transfer of that heat energy to proceed very efficiently.
Like any other mechanical heat exchanger (your refrigerator is probably the most common one that comes to mind). You are simply moving heat energy from one place to another. In your refrigerator, you are simply moving the Btu's of heat energy out of the milk and dumping it across the kitchen floor. That is why it blows warm air when it runs, which is nice in the winter but not so nice in the summer! That is why, in an old-fashioned refrigerator, those coils on the back got too hot to touch when it ran! To learn more abou how the refrigeration process works in a geothermal unit, take a look here.