They are the latter.
-ksen
It doesn't classify the articles into a "folder". All articles will show up on the same "Latest Posts" page, for example. The idea is that the poster of the article selects the Topics that best suit the subject matter of the article. The software also allows anyone to add additional topics to the article. If you want to search for articles that have been posted with that topic in the header, you click on "Topics", click on the topic name, and it will pull up all the articles that contain that topic.