This is used to ‘lock’ a cell in a calculation. When it is used a $ sign is included in the calculation next to a cell reference , e.g. A1 + $A$2. This means that this cell reference will not change if it is copied or autofilled elsewhere, it is locked.
If you are including a single cell in a calculation in multiple cells, you need to know this. E.g adding VAT to a whole list of products
The easiest way to do this is to create your calculation in the normal way but when you click on the cell you want to lock hit the F4 key, this will put in the $ signs.
Step by step to put the calculation in cell C2 in the picture is:
Now when you drag this calculation down into the cells below the first cell reference will change but cell B8 will not
To learn about relative cell referencing click here.
To learn more about Excel formulas click here.
This is covered in our Excel Essentials course.