The Baron Three Clubs is an alternative to the responder using Stayman over a 2NT opening bid.
The main advantage of this convention is that it becomes easier to reach minor-suit slams.
Maximum strength is thirteen points and the minimum depends on vulnerability and partnership agreement.
[1] When the opening is a bid of one of a suit, a 2NT response is given showing 16-18 points and a generally flat hand.
Opener responds 2NT with a minimum or at the three-level in his lowest four-card suit with a maximum.