What is a Swiss tournament?
A Swiss tournament is different than a Round-Robin tournament in that no players are eliminated. Every player will play every round, and the player with the highest number of points at the end of the tournament is the winner.
In a Swiss tournament, you don't necessarily play every other player. If there are a lot of players in the tournament, there may not be enough rounds for everyone to play everyone. Pairings try to put together players of similar rating in the first round. After the first round pairings are based on performance, those who won are matched with other winners, losers with losers. There may be some exceptions to avoid color repetition.