A collection of worksheets in Microsoft Excel is called a workbook. A workbook is another name for a document in Microsoft Excel. Workbooks are opened when Microsoft Excel is started, allowing the user to begin a new document or modify an existing one.
Workbooks by default contain three worksheets, but the number of worksheets can be increased or decreased at the user's discretion. Worksheets are arranged at the bottom of the workbook in tabular format.
Each individual worksheet in Microsoft Excel is a collection of cells into which data is entered. The data in the cells is manipulated by the user to perform calculations.