Fluid filled lines pump through pipes underground fairly deep and can both cool and warm as it runs through an electric looking furnace set up…But how it exactly works is beyond me. Does great with cooling in the summer, even when it was over 100 degrees back in 2021 the house stayed at 72. In the winter it will struggle if it gets down into the teens or lower and the emergency heating element will run. If single digits I have to run the propane fireplace in the morning for an hour or so, so the geothermal can keep up with the heating demand.
It’s basically just a heat pump with an underground heat exchanger loop instead of an air based one outside. The concept is that it is usually significantly warmer (winter) and cooler (summer) underground compared to outside air, thus enabling more efficient operation.