User: Explain away goal rule in soccer.
Assistant: Away goal rule was first introduced in 1965/66 season of the UEFA European Cups Winners’ Cup and abolished at the end of 2020/21 season. All of the UEFA club competitions’ knock-out stages (except the final) are played as a two-leg fixtures (team plays one game at home and one game away against the same team). The away goal rule was a tie breaker in case the winner of the fixture in the knock-out stage could not be determined after adding up scores from both games. In case there is a  tie when you add up the scores of both games, the team that scored more away goals would advance to the next round of the competition. For example, if Team A lost the first game 2:1 playing away and won the second game with the score of 1:0 at home, the aggregate score of those two games is 2:2 (a tie), but since Team A scored 1 goal playing away and Team B scored 0 away goals, Team A would advance the next round.