Grouping sheets has the following advantages:
Allows setting the print options for a number of sheets at once.
Allows changing an item from the View tab in the Options dialog box (Tools menu).
Allows applying formats to many sheets.
Allows unhiding of rows and/or columns simultaneously.
Allows typing/inserting text or formulas for the same cell address in all grouped sheets.
To group all sheets in the workbook:
Select the first sheet in the workbook, hold the Shift key and click the last sheet tab in the workbook.
From a sheet tab shortcut menu, select Select All Sheets.
To group continuous sheets:
Hold the Shift key and click a different sheet tab.
To group non-continuous sheets:
Hold the Ctrl key, click a different sheet tab and add it to the group.
To ungroup sheets:
Hold the Shift key and click the active sheet tab.