text: **Functions Overview**
  
  Functions are simply pre-programmed formulas already provided for you in Excel which can perform 
  calculations covering a wide range of categories including statistics, date and time arithmetic, financial 
  calculations, lists, engineering, and more. 
  Just like normal formulas that you create, functions must start with an***equal sign***. The equal sign is 
  then followed by the***name***of the function (usually a descriptive name which indicates the purpose of 
  the function). Most functions also require additional information known as***arguments***which are 
  supplied to the function in brackets after the function name. Functions are therefore written as follows: 
  **=*name*(*arguments*)**
  The arguments are quite often cell or range references that contain values that can be used in the 
  function. For example, the commonest function is the***SUM***function which, as its name suggests, is 
  used to sum or add values together. If you wanted to add all of the values in the cells from***B10***to***D15***
  you would write this function as: 
  **=SUM(B10:D15)**
  As you can see this is much simpler than writing your own referential formula which would look like: 
  **=B10+B11+B12+B13+B14+B15+D10+D11+D12+D13+D14+D15**
  Imagine writing and proofing a formula where you had to add 200 cells! 