Inherence, also known as "something a user is" or "something you are" refers to some sort of unique trait about a user. Examples are facial recognition, fingerprints, retina scans, etc.
Multi-factor authentication (MFA; two-factor 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. MFA protects personal data—which may include personal identification or financial assets—from being accessed by an unauthorized 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.