Welcome to the forum. When there is a new post in a thread it gets "bumped" to the top of the thread list. So for example if I was selling a cue but instead of creating a new thread every time disappeared off the first page l could just reply with "bump" to bring it back to the top. Hope that makes sense
they bump in the forsale threads so their ad it up top, because if your ad falls to page 4 not as many people look at it, in the other forums it dosent happen often.,
I was going to reply that a bump was those things you see all the guys running into the men's room to do before their turn at the table in all the amateur tournaments.
But I guess your answer is probably more appropriate.