Pump-action is one of the most popular, where the user slides the forearm back and forth to eject spent shells and load new ones. These are known for their reliability and simple design.
Semi-automatic actions are also common, using either gas or inertia operating systems to automatically cycle shells. Gas-operated shotguns use the expanding gases from firing to cycle the action, while inertia-driven systems use the gun's recoil.
Break-action shotguns remain popular, especially for hunting and sport shooting. These hinge open at the breech for loading and are available in single-barrel, side-by-side, or over-under configurations.
Less common but still available are bolt-action shotguns, which operate similarly to bolt-action rifles. These are typically used for specific purposes like slug hunting.