The worksheet on your screen is just one sheet in the current file, which is referred to as a workbook. By default, each workbook contains 16 sheets but this number can be increased to a maximum of 256 sheets. Well, one can have tabular data on one sheet, graphs of that data on another sheet and macros on yet another sheet. For each sheet in a workbook, Excel displays a tab, like a file-folder tab above the Status bar at the bottom of the screen. There are also tab scrolling buttons to the left of the tabs themselves.
Most worksheets consist of tables of numbers, called values in spreadsheet jargon.
Various calculations can be performed on these values with formulas. You can also enter dates, times and text. In a moment, you will enter a lot of values into a spreadsheet. Since humans err, it is best that you know how to correct your mistakes. When you make a mistake, you can click the cell contained the error and simply type in the correct entry.