I have no idea what they mean. I’ve been active on this site for a year. At first, when I asked a question, or responded to a question-maybe both-I tried to fill out the “topic tags”. I think I stopped doing that when I realized that no matter what tags I put on a posting, I couldn’t see a difference as to where/how that posting showed up.
I made a guess that they were there for the editor(s)-to help in sorting out where postings might be relevant in different discussions. Poor grammar there, but…maybe you get my point.
Basically, I’m curious as to the answer to your question also, just not as curious as you are!