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.

2FA Authentication takes place when someone tries to log into a computer resource (such as a network, device, or application). The resource requires the user to supply the identity by which the user is known to the resource, along with evidence of the authenticity of the user’s claim to that identity. Simple authentication requires only one such piece of evidence (factor), typically a password. For additional security, the resource may require more than one factor—multi-factor authentication, or two-factor authentication in cases where exactly two pieces of evidence are to be supplied.^[1]

(https://en.m.wikipedia.org/wiki/Multi-factor_authentication)