I spent some time wondering what the meanings were of all the icons at the left of a topic title on the new (version 3.0) software. Bizarrely, the makers of phpBB3 don't include the meanings, but I managed to find this link that tells the whole story (you'll have to scroll down past the first 8 or so posts)...
https://www.phpbb.com/community/viewtop ... 4&t=587802
Topic Icons
Moderator: Moderators
Topic Icons
It's an ill wind that never blows at all.