Metadata is simply information about computer files and related records. Consider, for example, a Microsoft Word document on your computer. The following pieces of information about the Word document all count as metadata:
This information is useful for a variety of purposes. For example, you might want to sort the items in a directory so that the most recently-modified files are at the top. This helps you locate documents that are current projects or works-in-progress. As another example, you might want to know the created and modified date for a Word document you receive in discovery so that you can confirm the document hasn't been modified since it was originally created.
The definition of metadata above as "information about computer files and related records" is pretty loose and not very precise. That's on purpose. Trying to nail down a precise definition of metadata isn't helpful. It's not important to decide whether the name of a computer file counts as metadata or, instead, as part of the file. The same goes for tracked changes and comments. The key thing to know is not whether these items count as metadata, but that they are always useful and sometimes very relevant.
But there's one distinction that it pays to be very clear about ...
The best way to grasp this distinction is to inspect metadata in some of your own files. You can view system metadata in Explorer (Windows) or Finder (Mac), and you can view application metadata by opening files in the applications you used to create them.
Not true. Metadata often counts as substantive evidence. For example, comments in a Word document can show the drafter's intent. The same with tracked changes and formulas in Excel. Further, metadata is extremely useful for authenticating evidence because it often shows the author and creation date for files. Digital photographs often include GPS coordinates. Without metadata, you'd have to authenticate Word documents and digital photographs based only on testimony.
Not really. Application metadata produces itself if you produce files in native format. System metadata is a bit more difficult, but some parties will agree to forego system metadata. In any case, the probative value of metadata makes it worth some extra effort or cost.
Please don't do this to documents that count as evidence in a case. That would constitute spoliation because it would change the evidence and destroy important data. On the other hand, some lawyers like to scrub metadata from Word documents so that the other side doesn't see metadata such as the document author or the total time spent editing. Still, it's hard to see what bad things would result from the other side seeing this information.
Nope. There's nothing sneaky or unethical about carefully reviewing evidence that you receive in discovery. In fact, the only thing that could be unethical with regard to metadata is not knowing about it and how it can be used to prove your case.