The difference between a revolver & a pistol

Sir Jayger gave us some information on how to differentiate a pistol from a revolver. A revolver has a rotating cylinder where you will put the bullet. The pistol don't have a rotaing cylinder and it is close unlike the revolver. If you fire a gun, gun powders are more present in your hands if you used a revolver, because a revolver is an open one. Sir showed us a Caliber .40 pistol and a Caliber .38 revolver to see the difference. The caliber indicates the diameter of the gun in inch. Example, a Caliber .40 pistol has a diameter of .40 inch.