After you create the group, the word "group" appears in the title bar of the workbook. Once they are grouped you can format one worksheet and all of the worksheets will have the same formatting. You can insert a row in a worksheet and the same row will be inserted into all worksheets. This is a great tool when you need for all of your worksheets to have the same formatting.
How many Worksheets can I Create within one Workbook? Prior to the release of Excel 2007 users could only create 255 within one workbook. However, since the release of Excel 2007 users can now create as many worksheets within one workbook as the memory of the computer can handle. Even if the user does not have access to one of the newest versions of Excel such as Excel 2007 or Excel 2010, they can still make as many worksheets as they would like, but earlier versions of Excel will require more workbooks.