https://hls.harvard.edu/dept/its/what-is-metadata/

What is metadata? Metadata is information stored within a document that is not evident by just looking at the file. It is an electronic “fingerprint” that automatically adds identifying characteristics, such as the creator or author of the file, the name of individuals who have accessed or edited the file, the location from which the file was accessed, and the amount of time spent editing the file. In addition to data that is automatically added to a document, there is user-introduced metadata, such as tracked changes, versions, hidden text and embedded objects.

Every time you create, open or save a Microsoft Word document, hidden information is created and stored within the document that you may not want others outside of your organization to discover. Hidden information can also reside in other Microsoft application files, such as Excel spreadsheets or PowerPoint presentations and includes:

Your Name and Initials, Company Name, Computer Name, Location of Document on Local or Network Server, Attached Template, Hidden Text, Comments, Track Changes, Non-Visible Portions of OLE Objects, File Properties and Summary Information, And more …