The Microsoft Data Classification and Recommendation Service detects the categories of data you've inserted in your Excel ...

The Microsoft Data Classification and Recommendation Service detects the categories of data you've inserted in your Excel workbook (e.g., cities, countries, image), sends those data categories online to Microsoft and recommends other sets of similar data that may be of interest to you.  The actual content from your workbook is not sent.

To enable the Recommendations Service and send data categories to Microsoft, select the ‘Yes' button, below — in the future, data categories will be sent when you click the "Suggest Related Data" button in the Excel ribbon.  You will not have an opportunity to review the data categories before they are sent to Microsoft.  

You can disable the Recommendations feature at any time.