The saturated zone is the zone below the land surface where all the pores and cracks are saturated with water.

The water table is the upper boundary of the saturated zone.

The unsaturated zone is the zone above the water table where some of the pores and cracks are saturated with water and some are filled with air.

The vadose zone is the zone above the unsaturated zone where the pores and cracks are filled with air.

An aquifer is a layer of soil or rock that allows water to flow through it easily.

A confining layer is a layer of soil or rock that does not allow water to flow through it easily.

Hydraulic conductivity is the rate at which water flows through an aquifer.

Storativity is the volume of water that an aquifer can store.

Specific yield is the volume of water that an aquifer can release when the water table drops.

Darcy's Law is the equation that describes the flow of groundwater.

The unit of hydraulic conductivity is m/s.

The unit of transmissivity is m^2/s.

The unit of storativity is dimensionless.

The unit of specific yield is dimensionless.

Unconfined aquifers are the most common type of aquifer.