In Microsoft Excel, a function is a type of formula that allows the user to perform mathematical, statistical and logical operations more easily. While it is possible to create a unique formula, Excel offers users a variety of preset formulas that they term functions.
All formulas and functions must start with the equal sign in order to work properly. One of the most common Excel functions is AutoSum, as many people use Excel to calculate numbers. When a user employs this function, Excel automatically determines what data the user wants to add and offers the total sum of that data.