Microsoft Office 365 Portal - What is two-factor authentication and how do I set it up?

Explanation of two-factor authentication:

Multi-factor authentication is required on all mobile devices and private desktop devices (PC, notebook, Mac). Similar to e-banking, for example, the user is verified in two steps.
You log in with your password and another factor. The second factor can be an SMS sent to your phone or a confirmation request on the Microsoft Authenticator app. By default, authentication via SMS is set up for all SBB employees*; Microsoft Authenticator can be used as an option.

*If the mobile number is not published in the SBB telephone book, the second factor must be set up according to these instructions.

Setting up two-factor authentication:
Office 365 Support recommends setting up multi-factor authentication via Authenticator App.

Setup multi-factor authentication via Authenticator App --> https://sway.com/OBIdtFGDGVG9pWXn?loc=swsp

Setup multi-factor authentication via SMS --> https://sway.com/wRtSApzmmXnLCw3V

If there are problems, the setup can be reset via https://aka.ms/MFASetup.