When someone posts, it moves the thread to the top of latest posts. So a bump is a post designed to that.
'bttt' is another message that may be posted -- short for back to the top.
In addition, 'pings' are designed to flag certain posters over to a particular thread.
Thanks... but I still don't get it!
(sigh)
I will read, observe , and learn.....
humbly...