This was Liverpool’s brilliant goal against Manchester City in November 2015:
At the time, people were quite confused about why this was not offside when Coutinho poked the ball to Firmino.
Many people thought Firmino was offside because he was “behind the defenders” with only the goalkeeper to beat and he received a “forward pass.”
The direction of the pass is actually irrelevant, contrary to popular opinion.
FIFA Law 11 – “A player is in an offside position if:
• he is nearer to his opponents’ goal line than both the ball and the second-last opponent”*
Applying the letter of the Law, when the ball leaves Coutinho’s boot, Firmino is closer to the goal line than the second-last opponent, but he is not closer to the goal line than the ball. He is not in an offside position.
*The updated language now reads:
• any part of the head, body or feet is nearer to the opponents’ goal line than both the ball and the second-last opponent