All the bids are either weak major twos, or weak 5-5 types
2 Ds either weak in hearts or 5 spades and a minor
2 H is either weak in spades or 5 hearts and a minor
2 S is weak 55, with either both majors or both minors
A bidding convention is an agreement between two players on a different meaning of a bid in the card game bridge. These agreements are made so that partners can more quickly determine which contract, with both their cards, they can win together. Often, conventions are forged together into one, which is then called a bidding system.