A submachine gun is a type of firearm that is designed to fire pistol cartridges at a high rate of fire. It is typically lightweight and compact, making it suitable for close-quarters combat. Submachine guns are often used by military, law enforcement, and security personnel due to their versatility and ease of use. These weapons can be fired in both semi-automatic and fully automatic modes, allowing for rapid shooting. Popular examples of submachine guns include the Thompson submachine gun and the MP5. Their design often incorporates features like a shoulder stock and a magazine to hold multiple rounds.