What is false 9 formation?

More than a formation false 9 is a position. False 9 is a striker which drops slightly deeper to the danger area in between the defenders and midfielders.
https://youtu.be/dEAh2_P73A0

it leaves  centre-backs in two minds who can either follow the false 9, leaving space behind them for running midfielders or wingers to exploit or the full backs cover the space which leaves space for winger to easily go forward or leaving the false 9 to have time and space to dribble or pick out a pass.

In Guardiola’s tenure as Barcelona’s manager he moved Messi from the right to the center and made him play as The False 9 . Then, even in the International scene, teams started playing strikerless formations, Spain under Vicente Del Bosque proved as Cesc Fabregas played as false 9 in the Euro 2012 final. 

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