Away goals rule
A real life example would be in the 2011–12 UEFA Champions League, where Marseille and Inter Milan were playing in the Round of 16. Marseille won the first leg 1–0 at home, and lost the second leg 1–2. Because they were away from home, and they scored one goal (unlike Inter Milan, as they didn't score a goal when they were away from home), they won the match on away goals.