As you might have inferred, I am fairly new here and not yet familiar with the site's functions. I noticed there was a "1" indicated here (which has turned into a "5" during the time it took to write this post).
I am referring to this visual element:
I have checked my profile page, and while there have been new activity events, there weren't any I noticed that would correlate to this number. On the other hand, on some of my browser tabs -- specifically, ones subsequent to me examining my profile page and related pages -- the "badge" is no longer present.
This is confusing, as the tab that I had left alone to take a screenshot of updated to "5", whereas the remaining tabs did not show any change.
What causes the browser's notification badge updates on this site?