The following marks mark articles as (kinda) unread, in one form or other.
Ticked articles are articles that will remain visible always. If
you see an article that you find interesting, or you want to put off
reading it, or replying to it, until sometime later, you'd typically
tick it. However, articles can be expired (from news servers by the
news server software, Gnus itself never expires ticked messages), so if
you want to keep an article forever, you'll have to make it persistent
(see Persistent Articles).
Dormant articles will only appear in the summary buffer if there
are followups to it. If you want to see them even if they don't have
followups, you can use the / D command (see Limiting).
Otherwise (except for the visibility issue), they are just like ticked
Unread articles are articles that haven't been read at all yet.