Final answer:
An Excel formula is a user-created equation, while a built-in function is a pre-defined formula provided by Excel.
Step-by-step explanation:
An Excel formula is a user-created equation that performs calculations or manipulates data in a spreadsheet. It consists of mathematical operators, cell references, and functions. A built-in function, on the other hand, is a pre-defined formula provided by Excel that can be used to quickly perform common calculations or tasks.
For example, the SUM function is a built-in function in Excel that adds up a range of cells. So, if you have a range of numbers in cells A1 to A5 and you want to calculate their sum, you can use the formula =SUM(A1:A5).
In summary, an Excel formula is a user-created equation, whereas a built-in function is a pre-defined formula provided by Excel.