Enter passcode for Other iPhones. The message means you can enter your passcodes for other iPhones that you use to sign in the same Apple ID to sync all your iCloud data. The devices can be your mobile phones or your Mac computer.
Even if you forgot all the passcode, you won't lose all the icloud data. Check the video for more information.
The Text Tutorial: https://www.softwaredive.com/enter-pa...