Champions League
In short
The UEFA Champions League is the premier annual club football tournament for the top-division teams in Europe.
In plain words
The best football clubs from different European countries play against each other to find the best team on the continent. It starts with a league phase and ends with a knockout tournament and a final match.
A simple example
Real Madrid and Manchester City compete in the tournament to try and win the trophy and the prize money.
Why it matters
It is the most prestigious club competition in Europe and attracts the highest viewership in world football. Winning it brings massive fame and financial rewards to a club.
Easy to mix up
Do not confuse it with the UEFA Europa League, which is the second-tier competition for European clubs.