When you open the bidding with a suit bid there is a huge variety of hand types you might have. Your second bid (or rebid) gives you the chance to really help partner by narrowing that down – defining you hand as balanced or unbalabced and often giving an indication of strength as well.

If you have fit with the suit in which your partner has responded then you are going to show that straight away by raising that suit – by just one level if your hand is minimum or by bidding to the 3 or even four level with stronger hands.

Otherwise you show a balanced hand by bidding NT as shown in the panel above.  Now your partner can figure out how strong your hand is and whether the partnership belongs in part score, game or slam.