Revolver:
A revolver is a type of firearm, usually a handgun, that has a cylinder with chambers that contain cartridges. The cylinder revolves to align each chamber with the barrel and firing pin, putting the cartridge into position to be fired.
The firearm is considered “single-action” when the hammer must be cocked before the trigger can fire the weapon.
The firearm is “double-action” when pulling the trigger both cocks and fires the gun.