A keg is a small barrel. Kegs are often constructed of stainless steel. Kegs are commonly used to store, transport, and serve beverages (beer, vine and other alcohol and non-alcohol drinks).
A keg has a single opening on one end. A tube called a “spear” extends from the opening to the other end. There is a self-closing valve that is opened by the coupling fitting which is attached when the keg is tapped. There is also an opening at the top of the spear that allows gas (usually carbon dioxide) to drive the beverage out of the keg. The coupling fitting has one or two valves that control the flow of beverage out of and gas into the keg.