https://youtube.com/shorts/YRwvq9uueYU?feature=share
This is useful though I am not sure what they're using might be fake skin like piercers use to practice on...
The gun clamps the ear around where the hole will be, and then the spring loaded mechanism forces the post of the stud through the flesh of the earlobe.
Whilst some posts are pointier than others, none of the ones available for use with guns could be described as actually sharp. So theres likely a lot of crush and bruising. The gun can fail to force the post all the way through or in some cases (generally via poorly trained staff) the gun can cause part of the stud to end up inside the ear lobe (this also can happen if the lobe is infected and swells hugely).
The needle method uses a forceps clamp to clamp the ear around where the hole is marked to go, and then the needle is pushed through - as it is SO sharp it goes through very easily and so there is far less chance of bruising or crushing (though if someone is heavy handed with the clamps that can happen. It is less likely as its much easier to see the ear lobe with this method, there isn't a clunky gun in the way).
Then once the needle is through the earring is put in the end of the hollow needle, pull back and that pulls the post through the hole and the ball or sparkly front is screwed on. These flat back types are much more comfy, theres no pokey end sticking out of a butterfly cap, and they have enough room to allow for the ear swelling slightly.
Some people don't clamp - they use the back of the needle cap to provide resistance - you can see it clearly here ignore what he's doing threading the sleeper through both holes, its the same piercing type.
Here he uses a needle with a sleeve, remove needle, leave sleeve, push the post or the sleeper up the sleeve and pull that back to leave the post/sleeper in the new hole.
As you can see from the first video... this is quick and very low pain when done properly.
I had my first piercings done in a jewellers with a gun and they HURT, all subsequent piercings done in a piercers, with a needle, including tongue - verrrrrry little pain indeed and much faster healing too.