Named ranges can be great when you are writing formulas. Suppose if you assign the name WidgetPrice to cell A5, you can then use the name WidgetPrice in your formulas instead of A5. This will make your formula (and its purpose) easier to understand when you are working with them on a later date
This approach is great if you have not yet created any formulas. Suppose you already have a bunch of formulas in your worksheet, and they already reference cell A5 instead of WidgetPrice? You could, of course, select each formula and edit them to refer to WidgetPrice instead of A5, but that could certainly be a long process with a wide margin for errors.
The solution is to allow Excel to do the editing for you.
Follow the steps below to learn how:

 Define the named range you would like used in your worksheet.
 Select the cells that contain formulas.
 Display the Formulas tab of your Ribbon.
 Click the downarrow at the right of the Define Name tool (in the Defined Names group) and then select Apply Names. Excel will display the Apply Names dialog box.
 Click OK.
That’s all there is to it! Excel will examine your formulas and any reference to cell A5 is replaced with the name of A5, WidgetPrice.