Formulas are the heart and soul of a spreadsheet, and Microsoft Excel offers a rich environment in which to build complex formulas.

All formulas in Excel begin with an equal sign. The equal sign tells Excel that the succeeding characters constitute a formula rather than normal text.

To see how formulas work, begin by selecting blank cell A10. Then type =10+5 and press Enter. The value 15 appears in cell A10. Now select cell A10, and the formula bar displays the formula you just entered. What appears in the cell is the displayed value; what appears in the formula bar is the underlying value, which in this case is a formula.