Adds an additional level of protection beyond a single method of authentication. Think about passwords. By combining your password, which is a common single factor of authentication and is something you know, with a second factor, which is either something you have or something you are, you gain an added layer of security. This second factor could be something like a code sent to a smartphone, which is something you have, or a fingerprint, which is something you are. Just don’t get a false sense of security here. While it’s always worth doing, there are already 12 different ways two factor authentication can be defeated.