I am not a bridge player. I have a question about bidding in contract bridge. The question isn't about the mechanics of bidding or what is the ”best” bid given a particular hand. My question is about the ”communication process” in the bidding phase. I am aware that partners communicate information about the cards in their hands by bidding things like “1 Heart” or “ 3 No trumps” and hence to arrive at some “agreement” about how tricks they are likely to win in the playing phase . What I don't understand is all this information about bid is “public” so surely the opponents will make the same deductions as the partner as to the likely distribution of cards in the hands? So won't this end up with a sort of ”zero sum” where all players pretty much know what cards are held before the play starts and the playing of the hands is rendered pretty ”mechanical”? Also as I understand, bidding must be a fair representation of the cards held. Any attempt at “bluffing” or "misdirection" in bidding is considered at least “poor play” and at worst some kind of act against the whole ethos of contract bridge. Is that correct or an unfair characterisation?
Yes, you're right - there is no secret information shared by your partner but not with opponents, beyond the difference in ability of the two partnerships at deciphering the information. When I say "One Heart", everyone at the table knows that I have 12-21 points and 5 or more hearts.
Bridge isn't Poker, or any other similar game, where hiding your hand from your opponents is the skill portion of the game. In bridge, the skill is in deciding the best contract for your partnership, and then playing it correctly.
That's not to say you tell your opponents everything that is in your hand, though; in fact, this is one of the skills - knowing whether you should announce something that gives information away or not. Your opponents could be bidding for a contract, and you have one opportunity to make a call other than Pass, say; you could make that call, which both tells your partner something (say, what suit to lead), but also warns opponents of that same information - or you might not make that call, just "pass" instead, and conceal the information from all parties.
This is a (very old fashioned) extreme example, but many systems are designed at least in part to hide information from the defenders. Bids on the left, explanations on the right:
1NT-2D; 12-14 Balanced - Artificial game force
2NT-3C; No 4 card major or 5 card minor - show your shape
3H-4S; exactly 3 spades, 2 hearts, 4=4 in the minors (key!) - to play
Sure the defenders know a lot about opener's hand - 13 HCP give or take 1 point, exact shape - but that hand is going down on the table after the opening lead, so they'd know that all anyway. All they know about the closed hand is that it has enough strength for game (which, well, they're in game, so one would hope so) and his decision on where to play relied on partner's exact shape (so, almost always 5 spades, but could be weak in hearts with 4 spades, and now he knows that 3NT has a fatal flaw).
As the other answers noted, all bidding leaks information, which is useful on defence (or in declarer play, from bids made and not made from the defenders). During the play, similarly, defenders will pass information about their hand to their partner with their carding signals, and that is read by declarer as well.
The key is that the information passed to partner is worth more than the cost of giving it to the opponents (usually). Another key, given in particular by 'Forget...', is that even with all that information, declarer play is hard, and defence is harder.
This ability to pass information with a very limited set of calls is so critical in bridge (even if it's read by the opponents as well) that the premiere strategy for the weak side is to take away as much of that room as safely possible, to make it that much harder for the strong side to work out where to play. This is called "Pre-empting", and entire books have been written about it, and entire nights at the bar after the game are spent discussing the "finer points".
As far as deliberate misbids, you are correct, they are legal but frowned on in many circumstances (against weaker players, when not in contention (especially against friends who are), just for the [...] of it,...). They also can not be done too frequently, ethically (as partner will get a better idea than the opponents when you're lying, and what you have when you lie. Since the opponents are entitled to all information you know about your partner's bidding, either you have to tell them (and then there are issues about whether that agreement is legal) or you don't (and you have an unfair advantage).) How frequent is "too frequent" is a question for the ages, but I do it more than most, and I probably average two a year (over 4000 deals or so).
It's not commonly done even ignoring those restrictions because passing information to partner is so important that lying to everybody actually harms your score on average (which is why "when not in contention", et al).
But basically, "full disclosure" is a base rule of bridge. Playing it with that constraint is no different from not being allowed to leave the batter's box to get a better look at the pitch, or not being allowed to play the puck after crossing the blue line before it. The best players are "the best players playing within the constraints of the rules", in any game or sport.
Yes, it is a requirement that each partnership's agreements, both in Bidding and Play, must be available to the other side. However, by my estimate somewhere between 5 and 10% of all non-trivial calls by each side require judgement between two (or more) possibilities. These decisions are often the topic of long, occasionally even heated, discussion with partner and other colleagues after the game. Learning how to make these judgement decisions (which occur on at least half of all deals for at least one player at the table) is the learning process as one advance from novice to intermediate, to veteran, to expert, and perhaps beyond.
One of the most difficult lessons to learn is when not to make a call, even though you (at least nominally) have the right hand for it because it's the wrong time, or the wrong opponents. As a novice doing such usually results in a loss of more points than opponents were entitled to make at their own contract, through a doubled set. As one progresses through intermediate and veteran skill it is more common that such results in keying the opponent's play rather than bidding. If Declarer must locate an outstanding Queen, or protect against a bad break in in one opposing hand or the other, even an undue hesitation before passing may key the correct decision. It takes great discipline, skill, and experience to make each call and play in tempo, and avoid making calls which allowed by one's system would be inopportune at the current moment. That's where the great players pull ahead of those who are merely experts.
Finally, one must remember that all major tournaments are ten days long. Even in a team event with a six player team, where each player gets to sit out one third of the sessions, playing such a mentally intense activity for 7 hours a day, against top-level opposition, for ten days, is a significant test of endurance. One often hears intermediate players comment unfavourably on the errors made in the final sessions of major tournaments (and yes, I've been there and one that in my youth): "How could E. have missed such an obvious play?!" That's an easy thing to say when one plays 2 or 3 sessions a week against club opposition; try the same thing on the tenth day of 2 or 3 sessions per day against top-level opposition, like the champions do.
Bids not Intended to Make
The question says:
Also as I understand, bidding must be a fair representation of the cards held. Any attempt at “bluffing” or "misdirection" in bidding is considered at least “poor play” and at worst some kind of act against the whole ethos of contract bridge. Is that correct or an unfair characterisation?
This is quite incorrect. There are any situations in which intentionally bidding more than one can reasonably make, and failing to do so would be poor play. For example, if you have reason tom think, during the bidding, that you and your partner can take 8 tricks with hearts as trump, but your vulnerable opponents can take 9 tricks at no-trump, it is good play to bid four hearts, contracting to take 10 tricks. If your estimate is correct, your opponents will score 100 or 200 points for setting you (depending on whether your side is vulnerable) or if the opponents double you (as they probably should) they will score 200 or 500 points. But if you has permitted them to bid and make three NT, they would have scored 600, so 4H down 2 is a better result, perhaps much better
To Give a more detailed example suppose your partner o0pens one heart as dealeer, and your right-hand opponent bids 1 no-trump. Assuming Standard American bidding on both sides, you partner has shown about 13-20 high-card points (HCP) and your opponent 16-18 with a quick trick (stopper) in hearts, and a balanced distribution.
Now if you chance to hold S: xx H: KJxxx D: Qxxx C: xx
It is likely that you can take at least 8 tricks in Hearts, possibly more if your partner has more than the minimum promised, and it is very plausible though hardly certain that your opponents could make 3NT. An immediate bid of 4H v uts them off from 3NT, and will more often than not be a winning action, even when it goes down.
However, a bid that is too high would allow the opponents to make a score higher than any they might make by taking the contract. For example bidding 7H on the above hand and auction would be very unwise. How high to bids is a matter of skill and judgement, in light of one's own hand and the previous calls in the auction.
Public meanings of Bids
Now as to some of the other aspects of the question.
While the agreed meanings of all bids used must be known to or available to the opponents, there is often a significant range of hands that might make a particular sequence reasonable. Nor are all players capable of prefect play. The best way to declare or defend a hand, even given the knowledge revealed by the calls of the opponents, is often far from clear. In many cases there may bge two or more lines of play which could prove successful. Properly handling the timing of play, entries, transport between the two hands, and other options is often far from mechanical. Indeed this is one of the places where bridge skill can be decisive. A player who is good at play of the hand will have consistently better results than one who is only average, and will tend to be a winning player. Many books have bee written on the card-play involved, starting only at the end of the auction, advising how to analyze a hand based on the auction and the known cards, and how to achieve the best possible result in the circumstance. Once beyond beginner levels players strive to master these techniques, and to retain the needed focus and quick thought to apply them in actual play, as opposed to leisurely analysis of a paper problem. It is not at all easy.