Virusses them self don't fly around in air. They are carried in tiny droplets. A N95 mask is able to stop these droplets up to a very high percentage, thus giving you protection. A N100 (or was it N99?) mask will have slightly beter performance than the N95.

For the europeans here:
FFP2 is similair, but NOT identical to the N95
FFP3 is similair, but NOT identical to the N100