Bidding in contract bridge
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 &quot;One Heart&quot;, 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 &quot;pass&quot; instead, and conceal the information from all parties.