There's a bit of interesting wording on the PC controls for Destiny 2. The words "air move" are written and associated with the X-key. With the Destiny 2 PC Beta in full swing, it's no surprise that this hidden move is causing some confusion.
Destiny 2 Air Move

The “Air Move” that is attached to the X-key on PC is actually a Warlock-specific move. When using the Solar Warlock, known as the Dawnblade subclass, you are able to press X to initiate a special aerial maneuver.
Depending on what Attunement you're using, this will either perform the Icarus Dash or the Phoenix Dive. Pressing X when you have the Icarus Dash selected will cause your Warlock to dodge in whatever direction you're moving. This is excellent if you need to quickly get around a corner or jump that little bit further.

Pressing X when you have the Phoenix Dive selected (unavailable in the Beta) will cause your Warlock to drop from the air to the ground and restore health. Performing the Phoenix Dive when Daybreak is active will cause a massive explosion when you land. This air move is particularly useful against large amounts of enemies, as it deals damage in an area around you.
Be sure not to forget about the air move in Destiny 2, as it is extremely powerful, either getting you out of danger or immediately healing you. With the Destiny 2 PC Beta underway and the full release of the game happening next week, be sure to bookmark Tank War Room and the Destiny 2 hub so you can stay up-to-date on the latest news, guides, secrets, and more!