Captaincy.  

At some point in time, one partner, on any given hand, will take over 
as “The Captain” of  that particular hand.  Normally, that will be the 
partner of the player making the first “limiting” bid in the auction.  

So if the auction goes (with the opposition passing) 1H – 2C – 2D,  
Opener has limited his hand to one that has less than the requirements 
for a jump-shift, and his partner is now, basically, the captain of 
that hand and will make the final decision as to where it should be 
played.  

He could, however, throw the ball back into the opener’s court by bidding 
3H at this point.  2H would have been "to play" but 3H is invitational, 
asking the opener to bid 4H if he has a “good” hand.

Here is another example.  South bids two clubs, strong and forcing.  Left
Hand Opponent (LHO) overcalls two spades.  North passes.  South shows his
heart suit.  North bids four no trump, asking for aces.  North has taken
over control of this hand.  South shows three aces and North bids six 
diamonds.  This is the last makeable contract available to the North-South
partnership.  North has said "given all this I know about this hand, this
is our spot!".  South, unable to concede control, bids six hearts which
goes down three tricks for a minus three hundred score.  Six diamonds 
would have been worth plus 1370.  

Both Sides vulnerable.  East deals.
                              North
                              S: 9 2                  
                              H: 4           
                              D: K Q J 10 9 8 7 6 4 3
                              C: Void    
            West                             East
            S: K J 10 7 6 5                  S: Q 4 3        
            H: 9 6 3                         H: J 10 5     
            D: A                             D: 5                 
            C: Q 8 7                         C: J 10 5 4 3 2
                              South                         
                              S: A 8  
                              H: A K Q 8 7 2
                              D: 2         
                              C: A K 9 6  
          The Bidding:  
                   East   South     West   North                  
                   Pass    2C        2S     Pass
                   Pass    3H       Pass    4NT 
                   Pass    5S       Pass    6D  
                   Pass    6H  (All Pass)       
          Opening lead: AD

The point is that you must be willing to become captain and also to give
up captaincy in order to have a good partnership.