A geothermal HVAC system typically consists of an indoor air handler, an outdoor heat pump, and a series of underground pipes. The heat pump is connected to the underground pipes, which are filled with a water-based solution. This solution absorbs heat from the ground and transfers it to the heat pump. The heat pump then circulates the heated air through the air handler, which distributes it throughout the home. The system also works in reverse, absorbing heat from the home and transferring it back to the ground. This process helps to maintain a comfortable temperature in the home while also reducing energy costs.