what are aquifers?

Rain water and water from the other water bodies on the surface of the Earth seeps down into the soil and is stored as ground water. This passing down of water through the soil is known as infiltration. This infiltrated water accumulates in the deep underground, where a layer of impermeable rocks blocks the water from seeping down further. Such places that have an impermeable layer of rocks leading to the accumulation of water over it are known as aquifers.