The 95 stands for blocks "95% of small particles". That is not quite the same thing as specifically being 95% effective against covid-19.
Could be more, or less, depending on the properties of the particulate in question.
Wearing an N95 with exhaust valves practically defeats the purpose of general mask wearing (i.e. protecting others from yourself), so people need to be cautious of what kind they use if they are using that type of mask.
Interestingly, there were some studies of using various types of paper filter in cloth masks that achieve the practical effectiveness of N95, at least as it specifically relates to exhaled particulate transmission. (i.e. effective if everyone does it)