A filter compares your data to a value that you specify, and only displays the data that meets your conditions in the report. A parameter is an extension of a filter that allows the value to use in the filter to be passed in at run time.
Parameters allow the person viewing the report to decide which data to include or exclude based on attributes that you select when you design the report. See Working with Parameters for more information. Parameters can also be hidden and used for scheduling, specifying different values for different scheduled tasks. See Scheduling Reports for more information.