OK, worthy of research. Looks like it is some of all the above, and not 100% of any of it. Sort of like Flu vaccine.
Getting a COVID-19 vaccine can help protect you by creating an antibody response in your body without your having to become sick with COVID-19.
A COVID-19 vaccine might prevent you from getting COVID-19. Or, if you get COVID-19, the vaccine might keep you from becoming seriously ill or from developing serious complications.
Getting vaccinated also might help protect people around you from COVID-19, particularly people at increased risk of severe illness from COVID-19.
I said this was related to Moderna's vaccine. I'm wrong, it's about Pfizer's. Sorry.