Outline a list of data in a worksheet

From http://office.microsoft.com/en-us/excel/HA100244981033.aspx?pid=CL100570551033

If you have a list (list: A series of rows that contains related data or a series of rows that you designate to function as a datasheet by using the Create List command.) of data that you want to group and summarize, you can create an outline of up to eight levels, one for each group. Each inner level, represented by a higher number in the outline symbols (outline symbols: Symbols that you use to change the view of an outlined worksheet. You can show or hide detailed data by pressing the plus sign, minus sign, and the numbers 1, 2, 3, or 4, indicating the outline level.) displays detail data (detail data: For automatic subtotals and worksheet outlines, the subtotal rows or columns that are totaled by summary data. Detail data is typically adjacent to and either above or to the left of the summary data.) for the preceding outer level, represented by a lower number in the outline symbols. Use an outline to quickly display summary rows or columns, or to reveal the detail data for each group.
You can create an outline of rows, an outline of columns, or an outline of both rows and columns.

An outlined row of sales data grouped by geographical regions and months with several summary and detail rows displayed.

To display rows for a level, click the appropriate outline symbols.

Level 1 contains the total sales for all detail rows.

Level 2 contains total sales for each month in each region.

Level 3 contains detail rows (only detail rows 11 through 13 are currently visible).

To expand or collapse data in your outline, click the "plus" and "minus" outline symbols.