A submachine gun is a type of firearm that is designed to fire pistol-caliber ammunition. It is typically lightweight and can be operated fully automatically or semi-automatically, making it effective for close-quarters combat. Submachine guns are often used by military and law enforcement agencies due to their compact size and high rate of fire. These weapons usually have a magazine that holds multiple rounds, allowing for rapid firing without the need to reload frequently. Popular examples of submachine guns include the Uzi and the MP5, both of which have been widely used in various conflicts and by special forces around the world.