Rolling Starts?

I was just recently viewing the Mens All-time 100m Lists and beside some of the times it stated “rolling start”, what exactly is a rolling start? what does it mean to have a rolling start?

As far as I know a “rolling start” can be either a falling start or a start where you walk into the sprint or step into it. Not exactly sure what they mean though. Relay split perhaps? That would be a “flying start” I suppose. :confused: