Here ya go - from Wikipedia
A Swiss-system tournament is a commonly used type of tournament where players or teams need to be paired to face each other for several rounds of competition. This type of tournament was first used in a Zurich chess tournament in 1895, hence the name "Swiss system". The Swiss system is used when there are too many players to play a round-robin tournament. It is also preferable to an elimination tournament if all of the players can play at the same time (e.g. as in chess but not in tennis, due to a limited number of tennis courts).
For the rest of the article, we will use the term player to refer to the parties involved. A team may be considered as a player when teams are playing against other teams.
A Swiss tournament goes for a predetermined number of rounds, with all of the players taking part in each round. In each round two players compete head-to-head. All players participate in the entire tournament – none are eliminated. The winner (and top places) of the tournament is based on the final scores of the players. The final score is based on the number of points they accumulated for each round. In some competitions, one point is awarded to the winner of a round; in others, a number of points can be earned each round.
The principle of a Swiss tournament is that each player will be pitted against another player who has done as well (or poorly) as him or herself. For the first round, players are paired either according to some pattern or randomly (according to common practice in that type of game or sport). For subsequent rounds, players are sorted according to their cumulative scores and players are assigned opponents that have the same or similar score to that point. One proviso is that the same players never oppose each other twice. There may be adjustments made to the natural order. For instance, in chess the pairings may be changed to equalize the number of times a player has been White and Black.