The core document of Excel is a workbook. Everything that you do in Excel takes place in a workbook. Beginning with Excel 2007, workbook “files” are actually compressed folders. You may be familiar with compressed folders if you’ve ever used a file with a .zip extension. Inside the compressed folders are a number of files that hold all the information about your workbook, including charts, macros, formatting, and the data in its cells.

An Excel workbook can hold any number of sheets, limited only by memory. The four types of sheets are

• Worksheets
• Chart sheets
• MS Excel 4.0 macro sheets, obsolete, but still supported
• MS Excel 5.0 dialog sheets, obsolete, but still supported

You can open or create as many workbooks as you want, each in its own window, but only one workbook is the active workbook at any given time. Similarly, only one sheet in a workbook is the active sheet. To activate a different sheet:

• click its corresponding tab at the bottom of the window
• press Ctrl+PgUp for the previous sheet
• Ctrl+PgDn for the next sheet.

To change a sheet’s name, double-click its Sheet tab and type the new text for the name. Right-clicking a tab brings up a shortcut menu with some additional sheet manipulation options.

You can also hide the window that contains a workbook by using the View -> Window -> Hide command. A hidden workbook window remains open but not visible. Use the View -> Window -> Unhide command to make the window visible again.

A single workbook can display in multiple windows: choose View -> Window -> New Window. Each window can display a different sheet or a different area of the same sheet.