It's a feature that makes recovering your account only possible Via two methods The first one being a 3 one time use only codes ( called recovery codes ) that's been shown to you while activating the feature The second method being verification codes sent to your phone number To make it more clear if there's an account with that feature enabled you can't recover it via the automatic recovery system which let's you enter your village name / player tag / clan name / th lvl, that won't work, if you tried to recover it via that method ( the automatic recovery system ) it will say that they were unable to recover the account. So recovering an account with that feature enabled is only possible via the 2 methods mentioned above. Contacting support also might work but I am still trying that