“Beyond Passwords: 2FA, U2F and Google Advanced Protection” is a rather lengthy, but insightful article on the subject of 2-factor authentication, multi-factor authentication, and other related options. It nicely explains which option is which and how it works, as well as clears a lot of confusion between these terms.
The article itself is not too technical, so it’s strongly recommended for anyone dealing with authentication, sensitive data, and security in general.