The server filters the data in the report output when you run a report with an input control. When properly applied, input control limits the data to what you want to see—and nothing more. When you run a report based on a Domain Topic that defines a filter, the server can render the filter as an input control.
If your system administrator has enabled the data snapshot feature, it is important to note that the default input controls - that is, the input controls as defined when the original Ad Hoc View-based report is run - will overwrite any changes made to them the next time you run a report. For instance, suppose you run a report, update the input controls, and then save the report. At a later date, you run a report from the Ad Hoc View source again. That new report will replace the report you ran earlier, and your input control changes will be lost.
To avoid this, save your updated reports with a different name than the default (Save As…). That way, when subsequent reports are run from the same source, they will not overwrite your report (unless they are given an identical name when saved).