With reporting you can create reports over the database data. Reporting is used for creating aggregated information, e.g. total sales per customer.
The difference between a datagrid and a report matrix is that the data shown in the report matrix is not stored in the database. Each time a report is created the data is retrieved from the database. The user can define a wide variety of data sets over the data presented in the report pane. Like for example aggregations, filters, etc.
The top section of the report pane can contain parameter widgets (drop downs and/or date range selectors) through which the end user can filter the displayed data, and a report button through which the end user can start the reporting.