Pivot tables are a truly amazing invention. They allow you to summarise, slice and dice data in many different ways without the need to write fiddly formulae.

Let's take the simplest of examples:

In this data, you will see that you have several entries for the various items that you spend your hard earned money on.

Lets say you want a summary of that.

Step1:
Select the data (that's Range B2 to C9) and go:
Insert => Pivot Table (XL 2007), then click OK
You'll now get a new worksheet:

Step2:
On the right, click on both "Expense" and "Cost", and there you have it, a summary of the data !

Training Video - Introduction to Pivot tables