The [Next] command takes you to the next un-read conference or topic in your hotlist. It's the primary way of reading stuff in ACME News. You set up your hotlist using the [Settings] page - it's the list of conferences you are interested in. Then when you click [Next], the system searches through those conferences for topics with responses you haven't seen yet. When it finds one, it first takes you to the conference page, and then another [Next] takes you to the first new topic in that conference. When you have gone through all the new topics, [Next] will bring up a "Done" page.
At that point you can start through your hotlist from the top again if you like, by just clicking [Next] again. If you get the "Done" page twice in a row then you are really truly done.
Your hotlist also gets reset back to the top if you go to the [Hotlist] page, or if you simply don't do anything for a few hours.