An absolute cell reference is one that refers to a constant cell and therefore overrides relative cell referencing, (which is the default in spreadsheets).
Absolute cell referencing is particularly useful for formulae that are being copied from one cell to another and are required to reference a constant cell.
Inserting a dollar sign ($) in front of the cell reference (e.g. $A$2) will make that cell absolute and ensure that the formula always references it.
Look at the example below.
The cost is always the same, but the number bought changes. The money in column references the cost and the number bought. It needs to refer to just one (constant) cost cell (A2) and to eight different number bought cells. (B2 to B9).
The picture below shows the formula in cell C2, which needs to reference cell A2 and cell B2.
The cost cell (A2) can be an absolute reference ($A$2), but the number bought cells need to remain relative.
In the picture below, the formula has been copied from cell C2 to cell C3. It now needs to reference cell A2 and cell B3. Notice that the absolute referenced cost cell (A2) has remained the same, but the number bought cell has retained its relative reference.
Now look at the picture below. The formula from cell C2 has been copied again into cell C4. The absolute cell A2 has remained the same, but cell B2 has changed to cell B4, keeping its relative reference.
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