This command is applicable for tables you store in Excel workbooks. If you have 2 tables with similar data, xlCompare can find duplicated rows. As a result of this operation you receive exactly the same rows on both worksheets.
On the screenshot about you see 2 tables with some rows on the right worksheet, highlighted with green color. These rows doesn't have matched items on the left worksheet.
To get only duplicated rows (without highlighting) use the Find Duplicates button on the toolbar. It is active on the screenshot above.
Please, note This command is visible on the toolbar ONLY when you select worksheet node or node under the worksheet - row, cell, grouping ...