Geothermal heat pumps are systems that use the stable temperature of the ground to heat and cool buildings. They transfer heat from the ground into a building during winter and reverse the process in summer, making them energy-efficient and environmentally friendly. These systems consist of a loop of pipes buried underground, a heat pump unit, and a distribution system for air or water. By utilizing the earth's natural heat, geothermal heat pumps can significantly reduce energy costs and greenhouse gas emissions compared to traditional heating and cooling methods.