It’s when you put a non striker as centre forward and he drops into the hole pulling their centre half’s out of position and you get runners / wingers in behind him.
The sort of tactic Man City or Liverpool might employ to pull teams out of their defensive position but **** me we’ve only just learned to pass to each other one step at a time
Messi was the original false 9. It’s become a bit trendier last few years as deployed by both City and Liverpool. I don’t think it will catch on at championship level.