What does "Shall not be infringed" mean in the Second Amendment? Because clearly it can be infringed and I feel like the authors really weren't precise with their language.

I apologize if this is a stupid question, but you can see why I am confused, right?

I'm not allowed to own an RPG (pretty sure).

If I'm convicted of a crime, I may not be able to own a gun.

Can children own guns? Not actually sure.

It just seems like there are plenty of examples where the right to own and bear arms is absolutely infringed. Can anyone explain?