A pivot table is a program tool that allows you to reorganize and summarize selected columns and rows of data in a spreadsheet or database table to obtain a desired report. A pivot table doesn't actually change the spreadsheet or database itself. In database lingo, to pivot is to turn the data (see slice and dice) to view it from different perspectives.
A pivot table is especially useful with large amounts of data. For example, a store owner might list monthly sales totals for a large number of merchandise items in an Excel spreadsheet. If the owner wanted to know which items sold better in a particular financial quarter, it would be very time-consuming for her to look through pages and pages of figures to find the information. A pivot table would allow the owner to quickly reorganize the data and create a summary for each item for the quarter in question.