A challenge is a request made to the holder of a competitive title for a match between champion and challenger, the winner of which will acquire or retain the title. In some cases the champion has the right to refuse a challenge; in others, this results in forfeiting the title. The challenge system derives from duelling and its code of honour.
These days, social networking has been challenged by asking users of these networks to post photos of theirs 10 years ago.
While many competitive sports use some form of tournament to determine champions, a challenge match is the normal way of deciding professional boxing titles and the World Chess Championship
Some racket sports clubs have a reigning champion who may be challenged by any other club member; a ladder tournament extends the challenge concept to all players, not just the reigning champion. At élite-level competition, there is usually some governing body which authorises and regulates challenges, such as FIDE in chess. In some cases there is a challengers’ tournament, the winner of which gains the right to play the challenge round against the reigning champion; in tennis this was the case at Wimbledon until 1922 and in the Davis Cup until 1972.source:wikipedia