Functions begin with an equals sign (=) followed by the function's name and its arguments. Functions perform particular calculations on the arguments, which are enclosed inside round brackets following the function name. The arguments can be numbers or references to other cells.
As an example, consider the simple function MAX. This returns that highest value argument. So:
will return the result 17, which is its highest argument. The arguments could also be references to other cells. For example:
will return either the number in cell A2 or B2; whichever is higher.
Please refer to the Microsoft Excel documentation for more information on functions.