You should protect your users and administrator accounts with more than one authentication method.
MFA is another layer of security for your users and administrators, it adds another code or approval that you can receive in a device that you possess - a phone, for example - to make it more difficult for attackers to steal your account. If they guess or brute-force your password, they still need the second code or approval to make it to your account.
Generally, every time you log in on a service, it will ask for your normal password and an additional code or approval. This can be retrieved through:
If you have Microsoft 365 Premium, Azure P1 or higher licensing you should use Conditional Access to set up MFA - read more about conditional access here: Do you use Conditional Access policies?
Once MFA is set up, you can see which method your users are using - go to Azure AD | Security | Authentication Methods | User registration details.
❌ Figure: Bad example - No Microsoft Passwordless phone sign-in registered
✅ Figure: Good example - Microsoft Passwordless phone sign-in registered
Your Authenticator App becomes a critical part of your day and being without it can seriously hamper your ability to work. The following steps can ensure that if for whatever reason you lose your setup, your can get back up and running as quickly as possible.
✅ Figure: Turning on Authenticator app backup on iCloud (or equivalent on Android)
✅ Figure: Good example - Email as a backup to Microsoft Authenticator App