To see what this looks like in detail, I invite you to view its presentation page at http://www.gandi.net/domain/whois
This service is free of charge and is made via your account management page. It requires just the acceptance of the Annex to the General Terms and Conditions of Domain Name Registration which you can read at https://www.gandi.net/contracts/en/whois/pdf/
Activation of this service in no way exonerates you from providing complete, exact and reliable contact information. Indeed, in the event of a verification either by Gandi or the registry, the non-disclosure of your current, full and accurate contact information can lead to the suspension or deletion of domain names managed under that handle. Also, this service is not one of providing an alternative contact address, of anonymity, or a forwarding of messages. There will therefore not be any forwarding of letters, messages or documents from people that try to reach you at our address.
This is therefore not a service just for convenience, but one that we provide for you as a way to help protect your privacy. The fact that it is free should also assure you that this offering is not just to make more money: is it a present from Gandi?
Finally, I would like to remind you that for the majority of European countries, individuals are already fully protected, as is true with .FR, or partially protected as with .EU (only the e-mail address is displayed).