Substitutes new_text for old_text in a text string. Use SUBSTITUTE when you want to replace specific text in a text string; use REPLACE when you want to replace any text that occurs in a specific location in a text string.
Text is the text or the reference to a cell containing text for which you want to substitute characters.
Old_text is the text you want to replace.
New_text is the text you want to replace old_text with.
Instance_num specifies which occurrence of old_text you want to replace with new_text. If you specify instance_num, only that instance of old_text is replaced. Otherwise, every occurrence of old_text in text is changed to new_text.
The example may be easier to understand if you copy it to a blank worksheet.
How to copy an example
Create a blank workbook or worksheet.
Select the example in the Help topic.
Note Do not select the row or column headers.
Selecting an example from Help
In the worksheet, select cell A1, and press CTRL+V.
To switch between viewing the results and viewing the formulas that return the results, press CTRL+` (grave accent), or on the Formulas tab, in the Formula Auditing group, click the Show Formulas button.