“F4” key provides you two different outputs depending on what you are doing currently in your excel.
If you are editing, then it will cycle you through the all three types of references, like – absolute reference, relative reference and mixed reference.
Refer below example for detail.
As displayed in below image in the selected cell of excel, we are first using the relative reference of Cell having Student A’s marks in English Subject. After pressing “F4” key it toggles and suggests the absolute reference of same cell and again by pressing “F4” key the mixed reference of the cell are suggested. If you are new to these terms of references – then you cango through this article to understand these in details.
In addition to toggling the reference of a cell, “F4” keys also repeats the last action performed in workbook. Although, this could also be achieved using “Ctrl + Y” keys.
Example: If you have just inserted or deleted a row or column in your workbook then by pressing “F4” key you can repeat the action of insertion or deletion of rows and \ or columns. Likewise if you have just pasted something in your workbook, then using “F4” you can repeat it.