Final answer:
An unconfined aquifer is not confined by any impermeable layer and allows water to flow freely, while a confined aquifer is sandwiched between impermeable layers and creates pressure that causes water to rise to the surface without pumping.
Step-by-step explanation:
An unconfined aquifer is a type of groundwater storage system where the water table is exposed to the atmosphere and not confined by any impermeable layer. It is typically composed of porous materials such as sand or gravel that allow water to flow freely. In contrast, a confined aquifer or artesian aquifer is a groundwater storage system that is sandwiched between impermeable layers of rock or clay, confining the water within the aquifer and creating pressure that causes the water to rise to the surface without the need for pumping.