LEARNING CENTER

Responder is the only one who can make a Negative Double. 

Reverse Drury is a convention bid by the responder after the opener opens a major in third or fourth seat. In addition to knowing who bids the convention, it's important to know if you play a convention like Reverse Drury after a double or overcall. 

Only overcaller can use the Unusual 2NT. Remember that either player can be the overcaller so, for instance, 

West	North	East	South
1	Pass	1	2NT

would be an unusual 2NT, but South here is the OVERCALLER (first to act for his side) not the advancer. There are other times that 2NT can have a similar meaning, but wouldn't be called "Unusual 2NT".  

Responder and Advancer. It's important to remember that once you open the bidding (or overcall on the lowest level), you can no longer show a weak hand. Responder and advancer, however, may have a fit and a weak hand. 

This is a convention used as part of a 2/1 GF system. It only comes into play as responder after a major-suit opening (and with no interference). 

Both Advancer and Responder can use Jacoby transfers. Responder uses it after a 1NT or 2NT opening (or 2C followed by 2NT). Advancer can use Jacoby Transfers after a natural notrump overcall.