An Excel workbook consist of worksheets. Think of it as using a notebook. You don't want to write everything on one sheet of paper. Excel gives you the option of having several worksheets so you can effectively organize your work into the worksheets. When using formulas in Excel, worksheets can display their power. You can have a summary worksheet linked to other worksheets in your workbook that provide data for the summary worksheet. For example, you can have a worksheet for 1st Quarter, 2nd Quarter, 3rd Quarter, and 4th Quarter. Compile your data for these quarters in separate worksheets. Once this data is compiled, you might want to summarize and analyze the results in a Summary worksheet in the front of your workbook. Another example of a linked worksheet can be seen here in this retirement savings calculator...An example of using only 1 worksheet is when you have limited data to display. An example of this might be a monthly budget.