At work I use pivot tables nearly every day. My work does not involve analyzing business or financial data and still I find pivot tables very useful in manipulating data sets, performing on-the-fly calculations, and preparing final reports.

So, what is a pivot table?

A pivot table is a data summarization tool found in data visualization programs such as spreadsheets (e.g. Microsoft Excel). Among other functions, they can automatically sort, count, and total the data stored in one table or spreadsheet and create a second table displaying the summarized data. Pivot tables are also useful for quickly creating cross tabs. The user sets up and changes the summary’s structure by dragging and dropping fields graphically. This “rotation” or pivoting of the summary table gives the concept its name. The term “pivot table” is a generic phrase used by multiple vendors. However, the specific form PivotTable is a trademark of Microsoft Corporation^[1]. – Pivot Table wikipedia entry

See the ExcelBlog.net In-Depth page for more information on Pivot Tables.