Bridge & other card games/Bridge
Please consider this case:
Opener bids 1 H with 5 of them and 13 points. Next opponent passes. Partner bids 1 spade with 4 spades and 6 points and next opponent passes.
Opener then bids 3 diamonds and opponents pass again. Is partner to take opener's re-bid as having 4 diamonds and 19 points or 4 diamonds and only 13 points. Please give me the reason for your answer if you don't mind as I would like to know.
Opener shows a hand of approximately 19 points or better. If opener has a weaker hand he can just bid 2D. This describes his distribution and keeps the auction at a lower level After all, if opener has only 13 points and responder has 6 points, they probably don't want to be wandering around at the three level or higher. A contract at the two level will probably be difficult enough to bring home. If you bid up the auction to higher levels you need to have the strength to justify that bidding.
If opener has 19 or more points, however, he probably wants to force the auction to the game level even if responder has a minimum response and he might want to investigate slam possibilities if responder has extra values. He shows this by jump shifting or skipping a level to bid 3D instead of 2D. The strength of opener's hand makes bidding at the three level reasonably safe.