Co-authoring documents - What is the difference between shared workbooks and co-authoring?

The distinction between 'Shared Workbooks' and 'Co-authoring' is crucial. The former, an older feature, permitted multiple users to collaborate on a workbook, but it had significant limitations. The latter, co-authoring, is a more recent development that has superseded shared workbooks. Co-authoring is accessible to Microsoft 365 subscribers through the Excel desktop client and Excel for the Web.