"Behind closed doors" is a phrase used to denote secrecy or privacy. It usually relates to a meeting or discussion that occurs between a select group of people who don't share the conversation with anyone outside the group. While the phrase may actually occur in a room with a closed door, no such physical reality is required. The phrase can as easily refer to private phone conversations or electronic communications.
In a government setting, for instance, meetings that are not open to the public may be said to occur behind closed doors or may be referred to as closed-door meetings. The phrase may also be used to describe a meeting or conversation that is closed to the media. Other examples include meetings of which no formal documentation occurs and business meetings that are not open to all employees. Most often, the details of such meetings are not disclosed outside the group, though decisions that are reached might be.
It is important to note that use of this phrase in relationship to a meeting or conversation, especially in a business or governmental setting, implies intentional exclusion. For example, a purchasing agent might close her office door when meeting with a vendor, simply to ensure quiet or to ensure that she does not disturb others around her. While they are technically meeting behind a closed door, this does not reflect the connotation of the phrase because her intent is not to prevent others from hearing the conversation or learning details of any arrangement being made.
Although the phrase is often used to imply that the participants are trying to hide something that should not be hidden, conversations and meetings may occur behind closed doors for a number of reasons, many of which are legitimate. For example, police may interview a witness behind closed doors both to protect the witness' identity and to keep the information she gives them secure. Likewise, a manager might conduct a performance review or discuss an employee's failure to perform in a closed-door meeting because it is good business practice to keep such conversations private.
Another common use of the phrase "behind closed doors" is to indicate that an individual's behavior and attitude are drastically different in private than in public. For example, an individual might appear to be generous and easy-going in public, but actually be an aggressive tyrant at home. Another person might be confident and outgoing at parties, but suffer anxiety and insecurity in private.