The term used for a natural underground water source is "aquifer." Aquifers are geological formations that can store and transmit water, serving as important sources for drinking water and irrigation. They can be replenished through precipitation or surface water infiltration, and they vary in size and depth. Groundwater from aquifers is critical in many regions, especially where surface water is scarce. Sustainable management of aquifers is essential to prevent over-extraction and contamination, ensuring a reliable water supply for future generations.