Thread:Support/Liquid bumps?

It is taking me a long time to get used to using liquid threads on the support page, learning new things being more difficult the older I get. I am finding the new link, at the top of the page, to new messages to be very useful, however.

I am puzzled by one thing, though. At the bottom of the edit box, when you 'add a reply' to a message, there is now an extra tickbox, ticked by default, labelled 'bump this thread'. What is this all about? (answer should be geared towards a computer-illiterate; funny replies would also be very acceptable!)