Dictionary

Authentication: is the act of proving an assertion, such as the identity of a computer system user. In contrast with identification, the act of indicating a person or thing’s identity, authentication is the process of verifying that identity. It might involve validating with personal password.
Authorization: is the function of specifying access rights/privileges to resources, which is related to information security and computer security in general and to access control in particular. More formally, “to authorize” is to define an access policy.
Multi-factor authentication: (or MFA) is an authentication method in which a computer user is granted access only after successfully presenting two or more pieces of evidence (or factors) to an authentication mechanism: knowledge (something the user and only the user knows), possession (something the user and only the user has), and inherence (something the user and only the user is).
Two-factor Authentication: (or 2FA) is a subset of MFA described above with only two different factors, i.e. something they know, something they have, or something they are.