Two-factor authentication adds a second step when you log in: as well as your password, you enter a 6-digit code from an authenticator app on your phone. Even if someone learns your password, they can't log in without your phone.
An authenticator app on your phone, such as Google Authenticator or Microsoft Authenticator.
After you enter your password, you'll be asked for the current code from your app. Codes change every 30 seconds. If a code isn't accepted, check that your phone sets its date and time automatically.
This protects your Client Area login only. DirectAdmin has its own two-step authentication. See Turning on two-step authentication in DirectAdmin.