Shaun is now feeling relatively confident, working with simple formulas. However, formulas will only help us with quite simple calculations. So in this video, we're now going to look at how to work with a different kind of calculation called the function. We're still working with our pushpin shipping data, but we're going to come down to the bottom of the screen, and click on sales 2016. Shaun has been asked to summarize the sales made by our account manages. His first job is to get the total sales of the last four quarters for each of our managers. The function that does the add operation for us, is called the sum function, and this function would do exactly the same thing as this formula. You will notice they look quite different. For one thing, there are no pluses or operators in the function, it is the word sum that tells Excel what we want to do. Another difference is, the brackets. The brackets and the function are not optional. Wherever you have a function name, you must have an open bracket, and wherever you have an open bracket, you must have a closed bracket. Another difference you'll notice, is the colon. Formulas don't contain colons, but functions very often do. The colon is a range operator. It means, work with all the values from B4, up to, and including E4. Let's have a look at how the function might work. So we're going to once again click in the cell where we want the answer to go. I could type the function as you saw previously, but there's an even quicker way. We're going to come onto our home tab of our ribbon, come to the far right, and click AutoSum. Excel is so clever. How did it know what I wanted to add up? Well, the truth is it didn't. Excel follows a simple set of rules. The rules for AutoSum go like this, look up, if there are at least two numbers above, add all the numbers until you hit text or a blank cell. If there are no numbers, go left, add all the numbers to the left, until you hit text or a blank cell. If there's nothing to the left, throw your arms up in despair. Fortunately, there were some numbers to the left and it's worked beautifully, let's try that again. So, I'm going to press enter, click AutoSum, once again, it's done what it needs to, click enter again, press AutoSum. This time, it looked up first, found two values, and added them up. Don't worry, if Excel doesn't get the right values, just go and explain to it that actually you want these ones, problem-solved and click enter. Now, actually we didn't have to do each of those. Just like with formulas, you can use your fill handle to copy functions. So, I'm going to click back home to F6, come to my fill handle, and drag back down. Now, for those people who like a shortcut, I now want to add up all of the totals in this bottom row. Instead of just clicking on the one cell, I'm going to click in B18 and drag across F18, I'm then going to come up to my AutoSum, and click. How quick was that? So now, you have a quick introduction to working with functions in general and some in specific. In the next few videos, we'll introduce you to some other useful functions.