It's a clock. It means they've been idle for a while.
I need to figure out how to shut off that horrible message announce noise.
I like it.
lol... If you click options there's a checkbox for 'Play sound for new messages'
Just uncheck it.
Not when you talk to me sweetheart.
I think they mean the chats that shows your friends you are online, on the bottom toolbar.
You can do group chats, too. It's on the right side of the bar.