General

What is it?
MFA (Multi Factor Authentication) enhances your security by requiring to enter a code (= a second factor, 2-Factor-Authentication/2FA). 
Why so complicated?
Unfortunately, security always comes with an extra amount of effort. Why does need an apartment a door lock? If I loose the key, I'm in trouble?!
Why so many different MFA types?
Each solution has it own advantage and disadvantage - again, unfortunately there is no one solution who fits all requirements.
Types of second factors
Supported at https://login.math.uzh.ch
There are more methods (SMS, FIDO, ...) but not supported at MATH/DM3L.
TOTP (Time-based One Time Passwords)
Codes are generated locally by a user's device (an authenticator app on a phone, KeePassXC, in-browser extension).
A new code is generated every 30 seconds.
Configuring TOTP requires to share a secret data between the server and the device: either by copying it directly or by scanning a QR code
Email codes
Codes are sent by the server to user's email and are valid several minutes. Only the last email's code is valid.
This method requires access to the email account.
Recovery (static) codes
A set of codes (usually 6) is shared between user and the server.
No expiration time.
Not practical for every day use, but can be treated as a backup method.