Every sport has to have some way of being able to properly and fairly break ties, and the away goals rule is one of soccer’s methods of breaking ties. This rule can only be applied when a team has played at both their home arena as well as at the away arena. In this case, the away goals rule means that the team that scored more goals at their away goal will win in the case of a tie. This is like away points counting for twice their worth when playing at away games.
Not everybody believes that an away goals rule is very fair and so not all soccer games will make use of this rule, even if the circumstances do qualify. Other methods are often sought after in order to settle ties and other such disputes.