A machine gun is a type of firearm designed to fire bullets automatically, allowing for rapid and continuous shooting as long as the trigger is held down. These weapons are typically used in military settings and can be mounted on vehicles or tripods for stability. They are known for their high rate of fire and can be fed by belts or magazines. Machine guns come in various calibers and designs, with some being portable and others requiring a crew to operate. They have played significant roles in warfare, influencing tactics and strategies since their introduction in the early 20th century, particularly during World War I and World War II.