What are the places where the groundwater is stored between layers of hard rock below the water table called? 

The correct answer is Aquifer.

Key PointsAquifer:

• It is a saturated area beneath the water table.
• It is basically an underground layer of water-bearing permeable rock, rock fractures, or unconsolidated materials.
• They are huge storehouses of water.
• Aquifers are of two types:
  • Confined Aquifer: It is an aquifer below the land surface that is saturated with water.
  • Unconfined Aquifer: It is an aquifer where the groundwater is in direct contact with the atmosphere through the open pore spaces of the overlying soil or rock.
• 

Additional Information

• Perched Aquifer:
  • It is a special case of an unconfined aquifer. This type of aquifer occurs when an impervious or relatively impervious layer of limited area in the form of a lens is located in the water-bearing unconfined aquifer. The water storage created above the lens is a perched aquifer and its top layer is called the perched water table.
  • Unconfined Aquifer:
    • An aquifer that is not overlain by any confining layer but has a confining layer at its bottom is called an unconfined aquifer. It is normally exposed to the atmosphere and its upper portion is partly saturated with water. The upper surface of saturation is called the water table which is under atmospheric pressure therefore this aquifer is also called a phreatic aquifer.

• Confined Aquifer:
  • It is also called an artesian aquifer. It is a type of aquifer overlain as well as underlain by confining layers. The water within the aquifer is therefore held under pressure. It is sometimes called a pressure aquifer also. If the aquifer has a high outcrop laterally than the ground surface there will be positive hydrostatic pressure to create conditions for a flowing well. Water from the well comes to the surface without pumping. The imaginary level up to which the water will rise is called the piezometric surface.