Groundwater refers to water that is stored in the soil or rock layers beneath the Earth's surface. It forms from precipitation, which seeps into the ground and fills up cracks and pores in geological formations such as sandstone, limestone, or dolomite. Groundwater can be extracted through wells for human use, including drinking water supply, irrigation, and industrial purposes. It is also an important source of water for many ecosystems and plays a vital role in maintaining the hydrological cycle on Earth.