The UEFA Champions League is a biennial association football competition organized by UEFA (Union of European Football Associations) that features top-tier clubs from across Europe. The competition includes a round-robin league phase and a double-legged knockout stage. It is one of the most prestigious club competitions in world football and is contested by the champions and, for some associations, a single or more runners-up of their national leagues.
The tournament was first launched in 1955–56, and initially consisted of sixteen champion teams from different European countries competing through a series of knockout rounds. Real Madrid won the inaugural championship and established itself as one of the best and most popular clubs in European soccer history.
In 1992, UEFA revamped the Champions League to add a group stage and a single-leg final while maintaining the rest of the structure. The changes made the competition more competitive and a bigger media attraction.
For the group stage, the thirty-two qualified clubs are divided into eight groups of four teams each, with a randomized draw and a coefficient-based seeding system to create balanced competition. The eight clubs in each group play two matches against each other, home and away, earning three points for a win, one point for a tie, and zero for a loss.
For the knockout rounds, except for the final, two teams are drawn against each other, and the team that scores more goals over the course of the two matches is the winner. If the teams are tied after normal time and extra time, the tie is decided by a penalty shootout.