The Trigger Safety
The most noticeable trigger safety on the Glock is the small switch on the front of the trigger. This switch must be pulled in order to further pull the trigger. The purpose of this safety is to prevent the trigger from accidentally activating; for instance, if the trigger were to be struck from the side, it would not fire since the safety switch had not been pulled.
The Firing Pin Safety
The firing pin safety is an internal steel pin located between the firing pin and the bullet in the chamber, preventing any contact between the two. The firing pin safety moves out of the way only when the trigger is pulled. As soon as the trigger is released, the safety is reactivated.
The Drop Safety
This second internal safety is in place specifically to prevent an accidental discharge from strong impact. The drop safety is a safety ramp that blocks the trigger bar from moving unless the trigger is pulled. This safety prevents the trigger bar from being jarred into firing by the shock of an impact. This differs from traditional pistols, which can accidentally fire this way.
The Trigger Finger Safety
This safety is not on the weapon, but relies on the shooter. The Glock pistol has no safety against human error, but is safe as long as there's no pressure on the trigger. Therefore, it's up to a shooter to keep his trigger finger off the trigger until he's ready to fire.
Manual Safety Locks
Keeping a manual safety lock over the trigger, when the pistol is in storage, can prevent unauthorized users (such as children) from using the pistol.