David, Striker Fired is the firing system used on Semi Automatic Pistols. They are all Semi Automatic which could be Striker Fired, Double Action Only, Double Action/Single Action, Single Action Action Only. In a striker fired gun, the hammer and mainspring have been eliminated from the frame. Instead, the mainspring has been moved up into the slide and acts on the firing pin directly. Except, now, the firing pin is called a striker. Rather than being hit by a hammer, it does the hitting itself.