O’Reilly has a posted a pretty good overview of Excel Pivot Tables on WindowsDevCenter. The summary is accurate:
The Pivot Tables tool is one of the most powerful yet intimidating features in Excel. Pivot tables allow you to quickly summarize and analyze large amounts of data in lists and tables–independent of the original data layout in your spreadsheet–by dragging and dropping columns to different rows, columns, or summary positions.
I’ve been using pivot tables with good success to analyze bug data from Bugzilla. As this article mentions, pivot tables are not that complicated, but they are not easy to learn. In a past job, I watched over someone’s shoulder as they went through it and realized how straightforward it is.