In contract bridge, various bidding systems have been devised to enable partners to describe their hands so that they may reach the optimum contract. Key to this process is that players evaluate and re-evaluate the trick-taking potential of their hands as the auction proceeds and additional information about partner's hand and the opponent's hands becomes available.
Hand evaluation methods assess various features of a hand, including: its high card strength, shape or suit distribution, controls, fit with partner, quality of suits and quality of the whole hand. The methods range from basic to complex, requiring partners to have the same understandings and agreements about their application in their bidding system.