Oh really!  I also know that to score, the ball has to enter the opponents' goal.
The rule of that game  is to score by getting the ball into the opposing goal.
I enjoy sports, but I wish I knew more about association football. Oh I see, well it's a team sport, and each side has 11 players.  More commonly, it's known as soccer or football. Ah yeah, I always call it soccer because in America we refer to a different sport as football.
The object of the game is to score by getting the ball into the opposing goal.