Both relative and absolute cell references are used in Excel formulas to tell the program which cells to consider for calculations. However, they behave differently when you copy or fill the formula across other cells.

Relative References:

* Default: These are the most common type of cell reference.
* Behavior: When you copy a formula containing a relative reference, the reference adjusts based on the relative position of the cell being copied to.
* Imagine you have a formula `=A1+B1` in cell C2. This adds the values in cells A1 and B1. If you copy this formula to cell D3, it will automatically change to `=B2+C2` because it moves one column to the right and one row down relative to its original position.

Absolute References:

* Created with $ symbol: You can make a cell reference absolute by pressing F4 after entering the cell address in the formula, or by manually adding a dollar sign ($) before the column letter and/or row number (e.g., $A$1, A$1, $A1).
* Behavior: Absolute references lock onto the specific cell location regardless of where the formula is copied.
* For instance, if you have the formula `=$A$1+B1` in cell C2, it will always refer to the value in cell A1 and add it to the value in B1, no matter where you copy the formula.

Here's a table summarizing the key differences:

| Feature | Relative Reference | Absolute Reference |
|---|---|---|
| Creation | Default | F4 key or manual ($) |
| Behavior when copied | Adjusts based on relative position | Locks onto specific cell location |

Choosing the Right Reference:

* Use relative references when you want the formula to adapt to its new position when copied. This is useful for creating patterns or calculations across multiple rows or columns.
* Use absolute references when you want the formula to always refer to a specific cell, regardless of where it's copied. This is helpful for referencing fixed values or data in another sheet.