Duplicate bridge is the most widely used variation of contract bridge in club and tournament play. It is called duplicate because the same bridge deal (i.e. the specific arrangement of the 52 cards into the four hands) is played at each table and scoring is based on relative performance. In this way, every hand, whether strong or weak, is played in competition with others playing the identical cards, and the element of skill is heightened whilst that of chance is reduced. Duplicate bridge stands in contrast to rubber bridge where each hand is freshly dealt and where scores may be more affected by chance in the short run.
Bridge boards, simple four-way card holders, are used to enable each player's hand to be passed intact to the next table that must play the deal, and final scores are calculated by comparing each pair's result with others who played the same hand. Bidding boxes are often used to facilitate the mechanics of bidding, prevent inadvertent passing of information, and minimize the noise level. Screens are used in higher levels of competition and were introduced to reduce the chance of passing unauthorised information to one's partner.
In duplicate bridge, a player normally plays with the same partner throughout an event. The two are known as a "pair". There are two exceptions: in team events with up to six members swapping partners for portions of the event, and in individual tournaments, in which players change partners for each round.
Read more about Duplicate Bridge: Bridge Organizations