The Arguments of Excel Functions
Memorizing the arguments that every Excel function takes would be a daunting task. Luckily, you don’t have to memorize arguments because Excel helps you select what function to use and then tells you which arguments are needed.
This figure shows the Insert Function dialog box. You access this great helper by clicking the Insert Function button on the Formulas Ribbon. The dialog box is where you select a function to use.
The dialog box contains a listing of all available functions — and there are a lot of them! So to make matters easier, the dialog box gives you a way to search for a function by a keyword, or you can filter the list of functions by category.
If you know which category a function belongs in, you can click the function category button on the Formulas Ribbon and select the function from the menu.
Try it! Here’s an example of how to use the Insert Function dialog box to multiply a few numbers:

Enter three numbers in three different cells.

Click an empty cell where you want the result to appear.

Click the Insert Function button on the Formulas Ribbon.
As an alternative, you can just click the little fx button on the Formula Bar. The Insert Function dialog box appears.

From the category dropdown list, select either All or Math & Trig.

In the list of functions, find and select the PRODUCT function.

Click the OK button.
This closes the Insert Function dialog box and displays the Function Arguments dialog box, where you can enter as many arguments as needed. Initially, the dialog box may not look like it can accommodate enough arguments. You need to enter three in this example, but it looks like there is only room for two. This is like musical chairs!
More argument entry boxes appear as you need them. First, though, how do you enter the argument? There are two ways.

Enter the argument in one of two ways:

Type the numbers or cell references in the boxes.

Use those funnylooking squares to the right of the entry boxes.
In the following figure, two entry boxes are ready to go. To the left of them are the names Number1 and Number2. To the right of the boxes are the little squares. These squares are actually called RefEdit controls. They make argument entry a snap. All you do is click one, click the cell with the value, and then press Enter.
Getting ready to enter some arguments to the function. 

Click the RefEdit control to the right of the Number1 entry box.
The Function Arguments dialog box shrinks to just the size of the entry box.

Click the cell with the first number.
This figure shows what the screen looks like at this point.
Using RefEdit to enter arguments. 
Press Enter.
The Function Arguments dialog box reappears with the argument entered in the box. The argument is not the value in the cell, but the address of the cell that contains the value — exactly what you want.

Repeat Steps 7–9 to enter the other two cell references.
The following figure shows what the screen should now look like.
Completing the function entry.The number of entry boxes and associated RefEdit controls grow to match the number of needed entry boxes.

Click OK or press Enter to complete the function.
The following figure shows the result of all this hoopla. The PRODUCT function returns the result of the individual numbers being multiplied together.
You do not have to use the Insert Function dialog box to enter functions into cells. It is there for convenience. As you become familiar with certain functions that you use repeatedly, you may find it faster to just type the function directly in the cell.