What is a 2FA?
2-factor Authentication aka 2FA is an approach to add another layer of security on the top of baseline layer of username and password. Generally, it is achieved by asking user to add another code when logging into a service which can be generated via a registered application (e.g. Google Authenticator, password managers, etc), sending a code to  registered mobile number or email address or other mechanisms like biosensor, touchpad, or other similar devices.