Revolver - Wikipedia

Revolvers were the first truly multi shot firearms. Previously a gun that could be quickly fired more than once used multiple barrels and firing mechanisms, which basically equates to welding guns together. A revolver works by having several firing chambers arranged in a circle in a cylindrical block which are brought into alignment with the firing mechanism and barrel one at a time. A single action revolver requires the hammer to be pulled back by hand before each shot. In a double action revolver, the trigger pull can pull back the hammer as well as release it.

Most commonly such guns have a five or six shot capacity (depends on the caliber) and each chamber has to be reloaded manually. This makes the procedure of reloading such a weapon slow (even with the help of such devices as quick loaders). The alternative is a replaceable cylinder.

Due to the simplicity of design, a revolver is cheap to make and almost guaranteed to work, first time, every time (the probability of jamming is almost zero). For these reasons, such guns are the most commonly owned weapons for personal self-defence.