Two-Factor Authentication (2FA) is an additional measure to protect your account. In addition to your password you will be asked for a second proof on login. This can be provided by an app (such as Google or Microsoft Authenticator) or a security device (like a Yubikey or your hardware wallet supporting FIDO2).
Best practice is to use FIDO2 Security device as a Two-Factor Authentication and add at least 2 security keys.
In this screenshot of BTCPay Server I have added three.
For a self-hosted solution not needing a 3rd party.