Multi-factor authentication (MFA) is a method of authentication that requires the use of more than one verification method and adds a second layer of security to user sign-ins and transactions. It works by requiring any two or more of the following verification methods:
A randomly generated pass code
A phone call
A smart card (virtual or physical)
A biometric device
Multi-factor authentication in Office 365
Office 365 uses multi-factor authentication to help provide the extra security and is managed from the Microsoft 365 admin center.