What is metadata in the real world? https://ssd.eff.org/en/module/why-metadata-matters
Usually we are thinking about in the context of communications, but files contain metadata as well. When it was created, where, by who... sometimes it even will tell you the type of machine.
Give me the GPS coords for this picture: https://exposingtheinvisible.org/ckeditor_assets/pictures/32/content_example_ibiza.jpg. I recommend this site: http://exif.regex.info/