A lot of definitions can be found in the web. More deeper information can be found In Wikipedia

Simple we can say that 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 to view it from different perspectives.

jqPivotGrid is a component that you can use with jqGrid to create a pivot grid.