Typically, the hammer strikes the firing pin which may fire a round, if there is a fresh round in the chamber.
In older pistols, the hammer can hit the primer directly (the tip of the hammer has the firing pin on the end).
Ring hammer.
Frame barrel hammer
A single action pistol, such as the 191A1 .45 Auto, requires that the hammer be cocked before the first shot. A Double Action pistol does not need to have the hammer cocked- pulling the trigger causes the hammer to rise and fall. Some are DAO- Double Action Only- the hammer cannot BE cocked, and must be fired from a "hammer down" position. These include the Para-Ordnance LDA pistols.
Frame barrel hammer
Stacey received a tongue lashing from Uncle Hammer because he was upset that Stacey had given away the pearl-handled pistol that belonged to Hammer's deceased wife. This pistol held sentimental value to Uncle Hammer, and he was disappointed that Stacey had not respected its significance.
That is the part which releases the hammer or striker to discharge the gun.
The sound of a pistol shot is the sound of the gunpowder exploding when it is ignited by the primer, which in turn was ignited by the hammer hitting it.
Often with a semiautomatic pistol, once a loaded magazine is inserted and the slide racked, you now have a pistol that is ready to fire: there is a fresh round in the chamber, the hammer (or striker) is cocked. This CAN be a dangerous situation, if the shooter isn't going to fire the weapon immediately. In the past, a person would have to CAREFULLY lower the hammer while pointing the pistol in a safe direction. If they slipped, they would fire a bullet accidentally AND their thumb would get hurt--mashed by the recoiling slide & hammer. A decocking lever prevents such accidents by LOWERING the cocked hammer to a safe position. Once utilized, if the shooter wanted to prepare the pistol for firing, they would have to: Manually recock the hammer, if the pistol were a single action only type, or, manually recock, or utilize the pistol's long Double Action trigger, if the pistol was a Double Action/Single Action type.
You need a gunsmith
Double action
You need a gunsmith
Single -Action