Contract bridge, usually known simply as bridge, is a trick-taking card game of skill for four players, usually sitting around a table, who form two partnerships, or "sides". The partners on each side sit opposite one another. The game consists of two main parts – bidding (or auction) and play; the rules of play are rather simple and similar to other trick-taking games. However, the bidding and associated conventions are much more complex, and represent the true learning barrier to new players. Also, there is an immense variety of techniques in play of the hand, whose effective use requires learning and experience.