When playing a "standard," i.e. non-big-club, system, the 2♣ opening usually is an artificial bid showing a strong hand of 22+ hcp (if balanced) or an unbalanced hand that only needs one "card" to make game. Traditionally, responder bids 2♦ and then, after opener has described their hand (balanced or with a good suit), responder gets to show that they have a "bust" (the second negative) or not.
But there's a popular response that shows a bust immediately by bidding 2♥. There are lots of reasons not to like this convention but the one I'm going to concentrate on here is that responder must make their decision before knowing anything about opener's hand. A common understanding is that 2♦ shows an ace, a king or two queens. I've never been comfortable playing that agreement because "two queens" might be just what partner needs for slam, or tram tickets. Let's take this example: ♠x ♥xx ♦Qxxxx ♣Qxxxx. If partner has a balanced 22, either (or both) of these queens might be useful. But suppose partner's hand is ♠AKQTxx ♥KQxx ♦Ax ♣K. How useful do you think your two queens are now?
For a real life example of the perils of this method, I present a hand from a friendly team match:
If partner shows a balanced hand, this could be quite a useful hand. We'd like to play game or slam in hearts by partner. But, what if partner has an unbalanced hand with spades? Our hand might not be so useful. Here's what happened (the auction ends in 6♠ if you can't see all of it):
On any lead but a club or diamond, the contract is down 2. On a club lead, there's a chance only if the opponents mis-defend. On a diamond lead, the contract is always down 1.
