Two clubs is the Stayman convention asking for a four-card major. Two diamonds and two hearts are transfers to hearts and spades respectively. Two spades is a transfer to three clubs which is either passed or corrected to three diamonds which, in turn, has to be passed.
With zero to four points, one may transfer to a six-card minor, and with zero to seven points, one may transfer to a major and pass, otherwise one just passes with a flat zero to seven points.
With eight to nine points, one may use Stayman or transfer to a major, then invite. Without a four-card or longer major, one may just bid two notrump to invite.
With ten to fifteen points, one can use Stayman or a major-suit transfer, then bid game. Without a four-card or longer major, one may just bid three notrump.
With 16 plus points, one investigates slam.
When partner opens one notrump, what does three clubs or three diamonds in response mean? These are free bids. One use of a minor at the three-level is showing a six-card minor with six to eight high card points and two of the top three honours. It invites partner to bid three notrump with a top honour in the minor or to pass three of the minor. WIth nine to 14 points and a six-card minor, one simply bids three notrump.
The bidding: North does not open the bidding with a weak two in diamonds because he has a four-card major. Furthermore, a weak two is not correct here because North could be a very strong dummy if partner opens one spade or one notrump. South, with 16 points, does open one notrump.
North does not have eight points, and therefore, cannot use Stayman. If he uses Stayman and then bids diamonds, partner will get an incorrect description of the hand. However, North can bid three diamonds inviting partner to either pass or bid three notrump.
South, with one of the top three honours, knows partner has the other two and bids game.
The Lead: The ten of clubs. Leading from the heart tenace is not recommended with only a four-card suit. One does not mind giving declarer a trick when setting up a five-card or longer suit. However, this is not the case when trying to set up a four-card suit. West can lead the ten of clubs and hope his partner can find a heart switch.
The play: Declarer will win six diamonds and two clubs for down one. If West leads a heart, declarer makes his contract.
Result: 3NT-1 for -50
Notes: All the bridge columns may be viewed at http://watsongallery.ca.