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A tournament is a competition involving a abnormally large number of competitors, who are all participating in a single sport or game. 

The structure of the map which a tournament run on is called a tournament tree, or just tree for short.

Tournaments work by dividing up the competitors in order to have less confusion and a set schedule to run on. This system of organisation is used in nearly all sports games, but just some being tennis, football, soccer, sparring, baseball, and more. Normally people rely on tournaments in order to work their way up to the major league or national league of sports due to their advancing and competitive nature. They work by pairing two teams or players against each other. They play until one side wins and then the losing side is eliminated from the tournament. Then next two winners play each other until only one player or team is left. This person is the winner of the tournament.  

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This is American Football League pre-match ceremony for the semi-finals, the second to last set of games.

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This is the same league, but the game is the last game, called the grand final.