2FA is an acronym for Two Factor Authentication. It is exactly what it sounds like – a way of authenticating users via two different methods, to add an extra layer of security.
2FA is viewed as being useful in preventing brute force attacks, wherein hackers try to ‘guess’ login credentials using automated bots.
Typically, the two methods involve authenticating via a traditional user name and password and a passwordless method like entering a numeric code (generated by authenticator apps) or logging in using biometrics like face scan, fingerprints etc.)
There are various WordPress security plugins like Solid Security that can help you implement this for your own website.