An aquifer is underground bed or layer yielding ground water for wells and springs.
Give me an example!
In order to get water to flow up the surface of the earth a well needs to hit an aquifer. Until the drill reaches this underground layer of water, the well will be dry.
An aquifer is a wet underground layer of water-bearing permeable rock or unconsolidated materials (gravel, sand, or silt) from which groundwater can be usefully extracted using a water well.