Views can be used to not only provide lists of contents, but also to provide aggregate functions on that content as well. You can enable aggregation by clicking on the No link next to the Use aggregation label, selecting the checkbox labeled Aggregate, and then saving either all displays or only the current display. Once you enable aggregation, all fields, filters, and sorting criteria gain a link next to them to set Aggregation settings.

Views allows you to perform grouping, counts, sums, minimum, maximum, standard deviation, and so on on any of these fields. Views leverages the database's ability to perform these functions and treat the output as the result of the query to be displayed, filtered, or sorted by.