Geothermal is heat energy from deep in the earth that is collected using special pipes buried underground. In some areas of the world, steam is collected and used to turn turbine generators. In other areas, pumps circulate water down several feet below the surface into the always-mild earth temperatures, where the water is cooled in summer and heated in the winter. This water is used in heat pumps to cool and heat homes and buildings and can also provide hot water.