A magazine, often simply called a mag, is an ammunition storage and feeding device for a repeating firearm, either integral within the gun (internal or fixed magazine) or externally attached (detachable magazine). The magazine functions by holding several cartridges within itself and sequentially pushing each one into a position where it may be readily loaded into the barrel chamber by the firearm's moving action. The detachable magazine is sometimes colloquially referred to as a "clip," although this is technically inaccurate since a clip is actually an accessory device used to help load ammunition into the magazine or cylinder of a firearm.
Magazines come in many different shapes and sizes from integral tubular magazines on lever-action and pump-action rifles and shotguns that may hold more than 5 rounds to detachable box magazines and drum magazines for automatic rifles and light machine guns that may hold more than 50 rounds. Various jurisdictions ban what they define as "high-capacity magazines".