While these rules of firearms safety are important, they are far more than words we want to memorize so it is important to discuss why they exist.
What we mean here is that you never want to unconsciously handle a firearm without knowing whether or not it is loaded. For example, if someone hands you a firearm or a significant other leaves one out, you must verify for yourself whether it is loaded or not. Until you do that, we have to assume there is something in the chamber. Following this rule, the only ''safe'' firearm is one that you have personally verified to be unloaded.
Assume there is a laser beam coming out of the muzzle. Anything that beam of light touches could be injured, destroyed, or otherwise hurt. Would that be acceptable to you?
This could be property like a vehicle, an animal on a ranch, or another person. This requires that we be aware at all times of where the gun is pointing. If you need to turn to talk to someone and can maintain a safe muzzle direction, great! If that is something that needs practice, then whenever you are not actively aware and thinking about the muzzle's direction, put the firearm down or holster it.
The truth of the matter is guns do not go off on their own. Sure some firearms can have mechanical failures, but the fact is, nearly all rounds being fired are the result of a conscious decision or negligent discharge. Negligent discharge meaning unintentional firing - before you were ready or expected to.
Until the sighting system of the firearm is oriented on or over what your eyes are looking at - what you have determined you are going to shoot - your finger should be off of the trigger and above the trigger guard. Not on the trigger but resting on the trigger guard can just as easily result in a negligent discharge.
To explain, think about the last time you were startled or lost your balance. Maybe you clenched your hands? That would be a natural response that many have. Now imagine your finger was resting on the trigger guard when that happens. Negligent discharge waiting to happen. So, keep that finger clear of the trigger guard and off the trigger until you have decided to shoot.
When a bullet leaves the barrel of a firearm it is traveling at exceptional speed. This speed means that round can travel for rather incredible distances at the right angle. Even the lowly 22LR can reach distances of a mile and further as extreme long-range shooters have demonstrated. As a result, understand what is behind your target and make sure the round will be stopped by something like a dirt or sand berm.
Following that, realize that rounds travel through things. They penetrate through paper, walls, thin metal like vehicle doors, and other barriers. Understand how to assess whether the direction you are firing is safe for you and others. Advanced coursework and competition can assist you in becoming better at this type of assessment.