After the opening 1-suit bid, the responder makes the second bid, which is one of the following 4 types of bids:
• SUPPORT the opener's suit by rebidding that same suit. The level of the re-bid indicates the reponder;s point count range.
• PROPOSE another suit to play.
• 1 NT - Keeps the bidding open - responder cannot support the opened suit and cannot propose a new suit. In this case, the opener can continue the bidding, or PASS.
• PASS - responder does not have enough HCPs to bid. If the bidding is still open, the opener can continue the bidding, or PASS.
Opener's Next Bid
Bid 3 - after the 1-Suit Opening
Depending upon the responder's bid, The third bid in this sequence
If the responder bids the same suit as the opener, the responder is SUPPORTING the opener's suit. The level of the responder's bid indicates the responder's point cout range. The partnership has found a suit to play, and will now find the appropriate contract level.
If the responder bids a different suit as the opener, the responder is PROPOSING a new 4+card suit. Since the responder's bid is made at the lowest level possible, the opener has only a vague idea of the responder's point count range. The partnership is stirll looking for a suit to play.