The knockout stages refer to a stage in a tournament where only winning teams are allowed to progress. In other words, it is a phase where losers are eliminated from the competition and only winners move forward. This term is commonly used in football (soccer) tournaments such as the World Cup or European Championships, but can also be applied to other sports like basketball or tennis. The knockout stages typically begin after the group stage of the tournament, where teams play against each other in a round-robin format and are seeded based on their performance. In the knockout stages, two teams face off in a one-off match with the winner moving onto the next round until only two teams remain to contest the final.