Face masks are used in a variety of environments. Often times, you will see them in a doctors office or clinical settings. Doctors and nurses in any operating room will use masks. Masks can also be used in higher risk settings, where you are trying to prevent either microscopic germs like the coronavirus, or noxious fumes from getting into breath.
Procedural masks are used primarily to block your own bodily fluids from dripping onto others in clinical environments. These are basic ASTM level 1 or level 2 masks.
Surgical masks are a bit higher of a quality, as they are intended to be used in surgical environments. These have an ASTM level 3 certification. A surgical mask will filter out a higher amount of bacteria at smaller sizes for a longer time, and N95 and higher classifications will filter out even more.