A machine pistol is a typically a -style firearm that can fire fully automatic or burst fire. Fully automatic means that the gun will continue to fire very rapidly so long as the trigger is pressed and held. Burst fire means that when you pull the trigger, a number of shots determined by the shooter will be fired (for some guns, this is three shots, fired very quickly). Machine pistols fire pistol cartridges. Machine pistols usually have the cartridges fed into the gun with a magazine, which is a rectangular box which holds the cartridges.