The default behavior for Microsoft Excel report exporting runs the entire report on a single Worksheet, whose name is the name of the report.

If a report contains Group Sections, an Excel report can be set to create a new Worksheet for each new instance of a group, by enabling this property.

Elements preceding the first group header will appear on the first page as normal. Each time a new group header is reached, the Excel document will break onto a new worksheet, containing all the contents of the group. The name of each worksheet will be the data field on which the group breaks. If the group breaks on a data category, the Unique Key field will be used to name the worksheet.

For more information, review the Excel: Grouping on Separate Worksheets article in the Knowledge Base.