Post exchange is a store or shop that the United States Department of Defense operates for active-duty and retired military personnel, and their families. The Army and Marine Corps usually call it a PX. The other services usually refer to it as a base exchange. On board vessels, the exchange is called a ship’s store. Major post exchanges resemble department stores. They sell a wide range of goods, from such personal items as toilet articles to automobile parts and home appliances. Many have beauty and barber shops.