What is closed diplomacy?

Closed-door diplomacy is when the negotiating parties do not reveal details about the process of the negotiation to the general public. This is contrast to open-door diplomacy, where the meetings are open to the press and the minutes are publicly released. The purpose of closed-door diplomacy is that it allows politicians to be more honest with each other about their needs from a treaty than they would be able to be if there were public scrutiny. Of course, it has the added advantage of stifling criticism of the negotiations since the particulars are unknown to detractors.