A pivot table enables you to summarize thousands or millions of records of data to a one-page summary in just a few clicks.
Suppose you have 400,000 records of transactional data. It is easy for some people to look at this and figure out that it represents $x million. But to learn some things about the data, you need to do some more analysis to spot trends in the data. A pivot table enables you to analyze trends in data without having to worry about formulas.
By using a pivot table, it is possible to create a number of views of your data, including the following:
Breakdown of sales by product
Sales by month, ...