Overview by David Bird

Each bid that the opener makes gives further definition to his hand. The opening bid merely names one of the opener's suit (usually the longest, or one of those with equal length). It says little about the strength of the hand, except that the values are held to open the bidding, and they are not worth a 2♣ opening.

The opener's rebid is critical. It begins to define the strength of the hand. With more than a minimum, for example, opener may jump-rebid his suit, or make a reverse bid. He may also rebid some number of no-trumps, or raise the responder's suit to an appropriate level.

So, this is an important lesson. The opener's rebid may be the path to a humble part-score, a game contract or a slam. It's important to get it right!