Originally pistols had the firing pin attached to the hammer. If the hammer was down and you dropped the gun or someone hit the hammer it would fire. To fix that and make the gun safe to carry they separated the hammer and the firing pin. Using this system the hammer cannot physical contact the firing pin. The hammer's energy is transferred to a bar which transfers the energy to the firing pin. The bar is only in position when the trigger is fully-pulled to the rear and lowers out of alignment when the trigger resets. If you look in front of the hammer or just behind the firing pin while you pull the trigger (gun unloaded of course) you may see the transfer bar elevating. That is the only safety that I know as called a "bar" safety. There are any number of safeties the "block" the hammer and/or firing pin. Without additional context, weapon type, etc., it is difficult to answer.

Its its own mechanism. Its designed to block the firing pin so that you must pull the trigger (which removes the blocker) so the gun will fire. Its intended to prevent accidental discharges if the gun is dropped. So if the trigger is not pulled normally, it will not fire, the gun will not shoot. Its just an added feature. Basically a bar blocking the firing pin. And the only way to remove that blocking bar so that the gun will fire is to pull the trigger. It shoots normally. Its only purpose is so if you drop it loaded, it won't shoot. The trigger must be pulled to allow the hammer to drop on the bullets primer. It looks like two triggers but they function as one.