When creating a report, you can filter your data in order to better manage your result. Visit the reports section and over there you will be able to view the filter button (1).
Clicking on that filter will open a pop-up window which will show all available filters for this report.
Note: You can inverse all filter for your report. Meaning that this will add a NOT operation to your filters. For example, assume that you want to get a report for all users that do not belong in the group 'Senior students'. Select the group filter with your group's name and the invert the filter from the corresponding option.