Revolvers are generally run by a cylinder. They are great for new firearm owners because they are more simple to operate and maintain than semi-automatic handguns. However, they hold fewer bullets and reloading can take longer.
How revolvers fire can be broken down into two categories: single-action and double-action. Single-action revolvers only fire when the shooter manually cocks the hammer. As the hammer moves back, it turns the cylinder that contains the ammunition, putting it into line to fire. You will need to repeat this every time you want to fire the weapon.
You can fire a double-action revolver either by cocking the hammer or by just pulling the trigger. Not cocking the hammer results in a longer trigger pull. If you want a shorter trigger pull, you can still cock the hammer manually. However, this may increase the firing time.