Plus how to use relative references
How to Use Absolute Cell Reference in Excel
Most people are familiar with using relative references in Excel. This is because cell references in Excel spreadsheets use the relative referencing method by default.
However, there are times when relative references become annoying. It changes cell references every time you copy cells or fill columns and rows. If you don't want references to change, you should use absolute references or mixed references (including relative and absolute references).
With an absolute reference, both the column and row references are 'locked', so neither changes when you copy or fill from that cell.