Which does a shotgun shell have that a cartridge does not?

A shotgun shell contains a plastic or paper hull that houses multiple pellets or shot, rather than a single bullet. Additionally, shotgun shells include a wad that separates the shot from the gunpowder and helps with the shot's dispersion upon firing. In contrast, a cartridge typically contains a single bullet, casing, primer, and gunpowder, designed for use in rifles or handguns.