A heat pump operates no differently than your refrigerator. A compressor in the heat pump unit absorbs heat from the ground loop in the winter (when the ground is much warmer than the outside air) and transfers it into the air in your building at a much higher temperature. A fan then circulates this hot air just like a typical heating system. Or, if a radiant floor is installed, the heat pump transfers this energy to the fluid that is running in the floor.
In the summer, this compressor operates in the other direction and absorbs heat from your building’s air, transferring it to the ground loop (when the ground is much cooler than the hot summer air). Conventional air conditioners operate similarly, but must reject the heat to the hot summer air, lowering their efficiency considerably