The three types of authentication are something you KNOW, something you HAVE, and something you ARE. A multifactor authentication uses 2 or more of these factors. A credit card is something you HAVE while a PIN is something you know.
Multi-factor authentication (MFA; encompassing authentication, or 2FA, along with similar terms) is an electronic authentication method in which a user is granted access to a website or application only after successfully presenting two or more pieces of evidence (or factors) to an authentication mechanism: knowledge (something only the user knows), possession (something only the user has), and inherence (something only the user is). MFA protects user data—which may include personal identification or financial assets—from being accessed by an unauthorised third party that may have been able to discover, for example, a single password.
A third-party authenticator (TPA) app enables two-factor authentication, usually by showing a randomly generated and frequently changing code to use for authentication.