Shotguns are different from rifles or muskets in that they fire multiple projectiles; most people know that. A rifle fires a single bullet each time the trigger is pulled. When a shotgunner pulls the trigger great bunches of pellets fly out the end of the muzzle. The pellets are actually round balls of lead, steel or other metal. Think BBs from a BB gun with the orbs varying in size, larger or smaller as needed.
How much larger or smaller? That depends.... “Buckshot” shotgun loads may only have the amount of pellets you can count on your fingers or fingers and toes. The number of projectiles in birdshot loads depends on the type of birds the shotgunner is planning to shoot. Generally speaking, the larger the bird, the larger the pellet. Goose hunters may load their guns with shells containing just over a hundred pieces of shot. Quail and dove hunters will likely choose shotshells with four or five times that number.
