This idea originated in John Nunn’s analysis of the game Petrosian – Unzicker 1960. Since the animation leaves out the context of the game, you may have a hard time understanding what’s going on at first, but hopefully the key point will become clear.
The key idea here is to consider opening lines before you storm the enemy position with your pawns. We can use pawns as battering rams to open space around the enemy king, but if the opponent has no counterplay available, why rush? Instead of letting our pawns loose immediately, it might be wise to open lines for attacking pieces beforehand. This happens here: Instead of playing 1. g4 right away, White plays 1. f4!, freeing the second rank for his rook, enabling it to join the attack faster once it’s rolling. Source: Secrets of Practical Chess by John Nunn.