The N95 mask is one of the nine particulate protective masks certified by NIOSH. "N" means not resistant to oil.
"95" means that when exposed to a specified number of special test particles, the particle concentration inside the mask is more than 95% lower than the particle concentration outside the mask.
The value of 95% is not the average, but the minimum. N95 is not a specific product name. As long as it meets the N95 standard and passes the NIOSH review, it can be called "N95 mask".
The protection level of N95 means that under the testing conditions specified in the NIOSH standard, the filtering efficiency of the mask filter material to non-oily particles (such as dust, acid mist, paint mist, microorganisms, etc.) reaches 95%.