A single-elimination, knockout, or sudden death tournament is a type of elimination tournament where the loser of each match-up is immediately eliminated from the tournament.
A double-elimination tournament is a type of elimination tournament competition in which a participant ceases to be eligible to win the tournament's championship upon having lost two games or matches. It stands in contrast to a single-elimination tournament, in which only one defeat results in elimination.
In a swiss format tournament, you play in the tournament for a fixed number of rounds. In each round, you are matched against opponents with the same win-loss record. There is no single winner in a swiss tournament.