Aquifers play a crucial role in the Earth's hydrological cycle by storing and supplying groundwater. These underground layers, often composed of porous rock or sediment, can hold significant amounts of water that can be tapped for agricultural, industrial, and municipal use. Aquifers contribute to the natural filtration of water and help maintain the flow of rivers and lakes, especially during dry seasons. They are vital for sustaining ecosystems and human activities dependent on freshwater.