In an artesian well, water springs from the ground by itself, without the need for a pump. The name comes from Artois, an area of France where this kind of well was first used. The Latin name for this region was Artesium.
Rainwater penetrates the earth until it reaches a layer of rock or soft sand. The water in this layer is under great pressure from the rock layers over it.
When a well or a fracture in the rock breaks through to the water table, the water flows forcefully upwards through the well to the surface, and can be used as drinking water.
Some desert oases are artesian wells.
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