You’ve probably seen the word “metadata” in articles about computer security, such as references to the government collecting only metadata from phone calls.
Metadata is a description of something, a title, if you will, but not the actual data itself.
Clickbait is mainly metadata. Here’s a Bizarro comic with a lot of metadata bumper stickers. The comic has enough of them that it should give you a good feel for what metadata is. [Side note: “clickbait” has become so common a word that it’s no longer written as “click bait.” But my spell checker hasn’t caught up yet. It still says I should use “click bait.”]
Today’s rule of thumb: The place for metadata in expository writing is in headings, not in the content.