Bedrock aquifers are, as the name implies, geologic bedrock units that have porosity and permeability such that they meet the definition of an aquifer (able to release water in quantities sufficient to supply reasonable amounts to wells). Water in these units is located in the spaces between the rock grains (such as sand grains) or in the fractures within the more solid rock.
Bedrock aquifers are fairly well defined in terms of their areal extent, and the units are considered to be connected hydrologically throughout their occurrence.
When an aquifer is separated from the ground surface and atmosphere by a material of low permeability, the aquifer is confined. The water in a confined aquifer is under pressure; therefore, when a well is installed in a confined aquifer, the water level in the well casing rises above the top of the aquifer.