Swiss-system is a tournament structure in which each round players or teams are paired against other players or teams on similar score to them.
Each participant in a Swiss-system tournament is awarded a number of points after each round depending on whether they win, lose or draw. At the beginning of each round, players are paired-up against other players on the same score as them. After a number of rounds, the player with the most points declared the winner. Typically Swiss-system tournaments have enough rounds so that it is only possible for one player to win every game that they take part in.
Many real world tournaments, including Yu-Gi-Oh! Championship Series and World Championship Qualifiers use this structure. In both of these examples, after a number of rounds of Swiss, the structure switches to single-elimination, which the top scoring players from the Swiss rounds take part in.
- en.wikipedia.org Swiss-system tournament