It basically means you will need a secondary device when signing in somewhere new with your Apple ID account. This would help prevent unauthorized use of your account, making the account much more secure.
This could have been activated with a password change.
If you want to revert (unenroll), then do so within the first two weeks of having it active.
TFA may be needed for some secure features.
TFA “trusted devices” can be set up on your Apple device, or on the Apple ID site.
You would get the verification codes on another Apple device, or on a mobile phone by SMS text message.
what the "two factors" are?
- Your account credentials (account name + password)
- The verification code