A shotgun is a type of gun. To make a shotgun work, gunpowder is lit by a primer inside of a shotgun shell. The gas from the burning gunpowder will push whatever is being fired out of the barrel. Usually a shotgun shell will have many small metal balls called "buckshot" or "birdshot". These balls spread out when they are fired. Sometimes a shotgun shell will have a bigger piece of metal, like a bullet, called a "slug".