gun newbie question here.......concerning the hammer on a revolver?

It's about accuracy, if you pull the hammer back instead of just pulling the trigger then you'll be firing it just like a single action. The less pressure it takes to pull the trigger and fire the gun, the more accurate you will be. The more lbs. of pressure required to pull the trigger for the hammer to release can cause you to accidentally pull the gun to the left or right at the last moment. So, usually when I shoot a revolver at the range I shoot it like a single action and pull the hammer back every time, but in a self-defense scenario just keep pulling and dump 6 bullets into them...