The UEFA Champions League is an extremely popular tournament in Europe by the top clubs in European soccer.  This competition takes place every year and is a big deal to both the clubs and the fans of the clubs.  The tournament works by teams having to qualify at first, then o the qualified clubs get put into the group stages.  There will be four teams in each group and all of the teams play each other twice.  Two clubs with the most points will advance to the round of 16.  Then a tournament tree is formed.

The two clubs that are paired will play twice and the team who wins on aggregate wins that round and proceeds to the next round.  Aggregate scoring is the better of two games, for example: if Real Madrid plays PSG and wins the first match 5-0 at home but loses away 5-1, Madrid would advance on aggregate with a score of 6-5.  But if Madrid wins at home 4-2 but loses away 2-0 PSG would advance because they scored more away goals. If both teams are even on aggregate, at the final match there will be 30 minutes of overtime and if no one scores in overtime there is a penalty shoot-out.

That being said, after the group stage is the quarter-final matches, then the semi-finals, and finally the final.  In the final, there is only one match, no aggregate scoring at this point.  The teams play two 45 minute halves with injury/extra time.  If no one scores within the 90 minutes it goes into overtime and if no one scores in overtime there is a penalty shoot-out.  Last year FC Bayern Munich defeated Borussia Dortmund in an insane 2-1 match.