the first column is whether you've posted in the thread, there are new messages, or it is just an old thread
the second column is an icon you can choose for your post located just above the Submit Reply button. (see i selected a green smiley)
yeah. i don't understand why everything is stacked this way. look at all that horizontal space between the username and join date/post count. is there a way to move the subject and time/number of the post into that space? does that make sense? you know? the yellow bar above your username and the red bar below it with the subject in it. those suck.