Just speculating...(I see the same thing), is it possible that you haven't read all of the posts within those categories and therefore the category would be BOLD indicating that there are posts within that you (or I) haven't read?
Although the autonomous car is not quite ready, a lights out print operation is something you can do right now if you have a comprehensive Print MIS (Management Information System). The advantages can put money on your bottom line. So what’s your next step? Link to Article