>>bloren+cd
The primary purpose of everyone wearing masks is so that people who are asymptomatic or pre-symptomatic minimize the spread of their droplets to everyone else. If the mask also protects you from sick people, that is an added benefit but secondary. Only N95 masks worn properly can guarantee protection for the wearer.
That means covering the mouth is most important because even breathing releases droplets. And the nose should be covered too, but only covering the mouth does help.