Air Gust is an airbending ability that pushes enemies back, allowing you to create space between you and your opponent. It also launches them into the air causing fall damage. It can be used on mobs and items.
As with all other abilities, there are two choices for Air Gust's level IV upgrade.
Extinguish: Destroy weak projectiles
The Extinguish upgrade allows you to block incoming weak projectiles (arrows potions, shulker balls, blaze fireballs, etc). Also it allows you to put out fires and deflect Ghast fireballs.
Vaccum: Pull enemies towards you
This vaccum basically reverts the main functionality of Air Gust, it pulls enemies towards the airbender. It allows you to close the gap within you and a ranged opponent or to bring the enemy to a trap (lava lake, spikes, hole, etc). It can also be used like a magnet to bring item towards you.