After partner has bid two suits, putting him back to his first suit or leaving him in his second suit is giving preference.
For example in the sequence: 1♥-pass-1NT-pass-2♦-pass-2♥, responder has given preference for hearts over diamonds. Since opener’s first suit will invariably be at least as long as his second suit, responder would also show ‘preference’ for opener’s first suit if his two holdings were of equal length. Responder would ‘prefer’ the second suit by passing or raising.
With 3 cards in opener’s second suit and 2 cards in opener’s first suit, responder may go back to opener’s first suit, an action known as giving ‘false preference’. This is partly because a 5-2 fit may play better than a 4-3 fit and partly because doing so keeps the bidding open in case opener is fairly strong.
