A drilldown report is a report that contains links to a second (or third) report that then filters data based on the initial report. In the example report below, the initial report shows a list of years and their total budget amounts. If you click on the drilldown column link (Year) you will get a second report showing the breakdown of budgets for that year by department. Currently, the only report type that can initiate a drilldown is a grid report but the report that is drilled down to can be any type of report including xsl or template.