If you hold 15 – 17 points and a balanced hand, then you should open the bidding with 1NT – click this link to read more about opening with a 1NT bid.
What should you do if you hold 12-14 points and a balanced hand?
You don’t hold enough points to open with a 1NT bid, so open the bidding with one of a suit and plan to rebid 1NT (don’t forget you need to hold a 5 card suit to open with a bid of 1H or 1S)
If partner bids 1NT, then pass as you know that you do not have enough points between you to bid for game.
You are West. A rebid of 2NT would tell your partner that you hold 18 points and invite them rebid if they wished. You don’t hold enough points, so you pass.
No Trumps rebids are some of the many topics available to members at www.nofearbridge.com