Multi-Factor Authentication, or MFA, is an approach to security authentication which requires that the user provide more than one form of verification in order to prove their identity and allow access to the system.  Authentication methods that only require username and password are susceptible to security threats because a malicious person only requires a single piece of information to access your account. The added security that MFA provides is requiring additional information to sign in: something the user has (phone/device).  Due to the increased complexity, authentication systems using a multi-factor configuration are harder to compromise than ones using only a single factor.

Standard login credentials are typically username and password.  If you are authenticating through a partner site - an online banking application, for example - you may be authenticated via Single Sign-On (SSO).  In that case, your SSO credentials replace the username and password