Artesian Well

Artesian groundwater is the same as any other type of groundwater the only difference is how it gets to the surface. 

An artesian well is simply a well that doesn’t require a pump to bring water to the surface; this occurs when there is enough pressure in the aquifer. The pressure forces the water to the surface without any sort of assistance.

An aquifer is a geologic layer of permeable and porous rock such as sandstone or limestone and that provides the water source for the artesian well.

The aquifer absorbs and stores water and in an artesian well the porous stone is sandwiched between a top and bottom layer of impermeable rock such as shale or clay. This causes positive pressure.

https://www.daleswater.co.uk/what-is-an-artesian-well/