A BB gun is most often a smoothbore air rifle that shoots perfectly round balls known as BBs. It’s pronounced “bee-bee gun,” and they are an American tradition. BB guns are simple and designed for recreational purposes (and sometimes for training purposes as well).
BB guns differ from pellet guns and airsoft guns significantly. Pellet guns are rifled and fire a somewhat conical projectile. They are typically more powerful than BB guns and can even be used for hunting. Some pellet guns get up to 35 in caliber, while BB guns always fire .177-sized BBs.
Airsoft guns typically shoot 6 mm plastic pellets and are safe to shoot at another person. Airsoft is a game based around shooting another person, and these guns are intended for that.
BB guns are not intended for shooting anything besides targets. They are not powerful enough to hunt with, but they are too damaging for shooting at another person.
BB guns are perfect as target guns and are remarkably affordable to shoot. The copper or steel pellets costs barely anything, and even CO2 pellets for semi-auto guns are incredibly cheap.
Some BB guns are designed to be training guns and mimic actual handguns. They make practicing draws, trigger control, and proper gun safety possible without a real firearm.