I see you’ve got terminology down, now let’s go for a little technicality.
Firstly, let me explain the “kick” of a gun. A “kick” is the feeling of the round leaving the barrel of the gun. Every gun has one, the impact of the “kick” depends on the caliber, make and type of gun.
Another way to describe a kick is the feeling of the gun exploding in your hand. Of course, the gun doesn’t literally explode, but it is a great burst of power that only lasts a second.
For example: A .45 mm hand gun with have a bigger “kick” than a .22 mm hand gun. If someone is a first time shooter and does not know what to expect, they would most likely drop the gun after firing it once due to the shock of the force being released in their hands.
Sniper Rifles are incredibly accurate and mainly used for long distance hits. They are also ridiculously heavy, as most rifles are, therefore, be prepared for a gigantic “kick”.
Sniper Rifles are special because they are so powerful (they need to be in order to have the same impact a .45mm would 10 feet away compared to the shell half a mile away), thus a stand is required to use it.
No matter what you will always need a firm holding to place the rifle (besides your grip) in order to prevent the gun from falling over after it is discharged and injury to your person. There are ridiculously powerful guns.
General rule of thumb is that you place the butt of the rifle next to your shoulder, just below your clavicle. I’m not very good at describing this position, so I suggest looking it up. DO NOT place it anywhere in the armpit area, dislocation is likely to occur. Depending on how prepare you are and the type of rifle being used (excluding snipers), bruising might occur.
You will be standing if you use a normal rifle, so make sure you are steady and prepared for the “kick” that follows after.
If you are using a sniper rifle, you will be on the ground or leaning against something. Some people have special rests for their snipers specifically to fire the gun from any spot. Point is: do not stand alone while firing this. You will get hurt.
Earplugs or Ear Protectors are your friends.
Safety glasses are also your friend to avoid shells from flying into your face.
Keep the safety on until you are ready to fire the gun.
If you are NOT currently firing the gun, whether it is loaded or unloaded, and it is in your hand, ALWAYS hold it with two hands and point it at the ground at your feet. DO NOT get distracted.
NEVER joke around with someone by pointing the gun at them. EVEN IF YOU ARE ABSOLUTELY POSITIVE THAT THE GUN IS TOTALLY UNLOADED, MAGAZINE OUT OF PLACE, DO NOT RISK IT. It is not funny. Even if the gun is on safety, do NOT do it. You could accidently switch off the safety or the gun could misfire despite the safety.
Lastly TWO HANDS. One on the side near the trigger and the other underneath. This is not the movies, do not attempt to fire a gun with one hand. Not only will your aim be incredibly off if you are inexperienced but you will also endanger yourself as well as others if you lose control of it.
Guns can be scary and if you ever feel nervous or uncomfortable about firing one, do not do it.