As discussed by Marty Bergen in Better Bidding with Bergen this is a fit bid
after a notrump opening. The main idea is that good fits must be shown, and even
opposite a bad hand such a fit will either play well or the opponents had a good
fit and contract for themselves. Therefore the difference between Advanced
Jacoby and Accept Jacoby Bid is that Advanced Jacoby does not accept the
transfer with a 4 card fit, while Accept Jacoby does not accept the transfer
with a 4 card fit and a maximum.
With 2/3 card support you always accept the transfer and bid 2 in the responders major suit. With 4/5 card support you bid 3 in the responders major suit with minimum, and bid 2NT or the suit with a doubleton with maximum.
1NT - 2D
2H two or three hearts.
2N 4/5 hearts; 4333 distribution
2S/3C/3D 4/5 hearts. Doubleton in bid suit; maximum
3H 4/5 hearts; minimum
1NT - 2H
2S two or three spades.
2N 4/5 spades; 3433 distribution
3C/3D/3H 4/5 spades. Doubleton in bid suit; maximum
3S 4/5 spades; minimum
1) if opener merely completes the transfer then he lacks four trumps.
2) further suit bids after bypassing the transfer start a cue bid auction.
3) responders rebid of the transfer suit is a retransfer to force the one notrump opener to bid the suit and thus become declarer.
3C 3H <- a retransfer to spades