A shotgun is a type of gun that can fire many small pieces of metal called pellets at the same time. When the trigger is pulled, the pellets are released from the barrel of the gun in a wide spread. Shotguns are used for hunting animals, shooting targets and skeet, and for home defense.
The spread of the pellets means that the shooter does not have to be as accurate of a shooter as with regular guns that fire a single bullet. This makes it easier for the shooter to hit their target. This also means that even if the shooter does not hit their target, the pellets will spread out enough to still do some damage.