In Excel, both formulas and functions are used to perform calculations and manipulate data, but there's a key distinction between them:

Formula:

* A user-created expression that combines various elements to perform a specific calculation.
* These elements can include:
* Cell references (A1, B2, etc.)
* Numbers (3, 10.5)
* Operators (+, -, *, /)
* Text strings ("Hello")
* Other functions

* Formulas are flexible and can be as simple or complex as needed.
* For instance, `=A1+B1` is a basic formula that adds the values in cells A1 and B1.
* You can't reuse a formula by itself; it needs to be recreated in each cell where you want the calculation done.

Function:

* A pre-defined formula built into Excel that performs a specific task.
* Functions have a particular syntax that needs to be followed, including:
* Function name (SUM, AVERAGE, VLOOKUP, etc.)
* Arguments (values or cell references) enclosed in parentheses
* There are hundreds of functions in Excel, each designed for a specific purpose, like calculating sums, averages, or performing lookups.
* Functions are reusable and can be easily copied to other cells.

Here's a table summarizing the key differences:

| Feature | Formula | Function |
|--------------------------|------------------------------------------------|-------------------------------------------------|
| Definition | User-created expression | Predefined formula |
| Flexibility | Can be customized | Specific purpose and syntax |
| Examples | `=A1+B1`, `=IF(A1>0, "Positive", "Negative")` | `=SUM(A1:A10)`, `=AVERAGE(B2:B15)`, `=VLOOKUP(C1, D2:F11, 2, FALSE)` |
| Reusability | Needs to be recreated | Reusable with different arguments |

In essence, formulas are like sentences you write using Excel's building blocks, while functions are pre-written vocabulary words that perform specific actions. You can combine both to create powerful and versatile calculations in your spreadsheets.