It all comes down to salt versus acid
I remember my grandmother doing some of this stuff when I was a kid. But, I never paid much attention to it.
Today?
SO, to debrief:
Brining = preserving and/or flavoring with salt
Marinating = preserving and/or flavoring with acid
Pickling = preserving with salt (fermented pickles) or preserving with acid (unfermented pickles)
Curing = all of the above
More @ What’s the Difference Between Pickling, Brining, Marinating, and Curing?