Since some pairs utilize nonstandard conventions, their opponents can ask for an explanation at their turn to bid or later at their turn to play if they see bidding they don't understand.
A request for an explanation of a bid should be directed to the partner of the player who made the bid in question. The proper form of the request is "Please explain".
The opponent is entitled to a full understanding of the agreement and all questions concerning the agreement should be graciously resolved.
These rules apply only to an understanding of special agreements between partners. This does not include inferences drawn from general bridge knowledge and experience. It especially does not include information as to how a player thought or acted in regard to the agreement. This would be unauthorized information.
If the meaning has not been discussed, "no agreement" is the proper response. If you've forgotten it, say so. You must not say such things as " I am taking it to mean ...". If an opponent asks you how you took partner's bid, you must not give this unauthorized information. Call the director immediately.
If you bid incorrectly in response to partner's conventional bid and an opponent asks for an explanation, you must explain the agreement. You must make no mention of the unauthorized information that you made an error.
In other words, you must fully explain the agreement, but never explain your thoughts or actions.
If your partner has been asked to explain your bid and does so incorrectly, you must give no indication. You have received unauthorized information of this misunderstanding and must proceed as if you hadn't heard it. If your side becomes declarer, you must call the director and fully disclose before the start of play. If your side becomes defenders, you must proceed normally and call the director to fully disclose at the end of play.
If your partner explains your bid correctly and you realize that you bid incorrectly, you have received unauthorized information and must proceed as if you hadn't heard it. In this case however, you have no obligation to disclose because partner's explanation was correct.
Unauthorized information is difficult to handle, so must be avoided as much as possible. When it occurs, you must bend over backwards to take no advantage.