Aggregate is a different way to say add up. When you add up an aggregate, the items you add together should be similar items. For example, in some soccer tournaments, they use aggregate scoring. Aggregate scoring adds together one team's goals both home and away against the total goals of an opposing team they played against in those two games. Aggregate is a useful way to track the total number of anything you decide you want your group to be.
Determine what you want to group. For example, assume a student takes a test with three parts. Each part is graded separately. The student wants to know his aggregate score.
Write out the numbers in the group. In the example, assume the student's respective scores were 45, 30 and 10.
Add together all the numbers in the group. In the example, 45 plus 30 plus 10 equals an aggregate score of 95.