Workbook() is a function provided by the openpyxl library in Python that creates a new Excel workbook object. A workbook is the main container for all the data and information in an Excel file, including worksheets, charts, and macros.

The Workbook() function initializes a new workbook object and provides methods to create, modify, and save the workbook to a file. The workbook can have one or more worksheets, each containing a grid of cells arranged in rows and columns.