What does aggregate means in European Soccer?

This only happens in a tournament. Aggregate is about the scores. If Arsenal scores 1 and Liverpool 2 at Arsenal's home, and Arsenal scores 1 and Liverpool scores 0 at Liverpool's home, Liverpool goes to the next round because Liverpool scored two at Arsenal's home. Away goals worth twice when the "aggregates" are tied. ......................Arsenal .................................Liverpool Home .................1.......................................... 2 Away ..................1 ...........................................0 In this case, Arsenal has 3 points and Liverpool has 4 points.