Beaver Island Michigan

Please help me understand what "bump" means?
Thank you

In online forums and other online discussion spaces bump is the word used to describe an action (e.g. a message post) so that a particular thread is returned to the top in the list of threads.

Any post responded to is a bump. Which moves it to the top of the list with each response. The bump is now being utilized to burry certain threads.

And I thought it was a dance in the '70's.

Thank you