You've learned Stomp! To use this ability, press A to leap into the air, then (toggle the left thumbstick down) to dive powerfully towards the ground!
Stomp is the 6th skill Ori learns, and makes them able to hit the ground hard and do damage to nearby enemies and objects, including the ground itself. This skill is earned after you've escaped the Ginso Tree, and walking towards east in the Thornfelt Swamp.
The Stomp Attack can be used to do more than break floors. Other possible uses include damaging enemies, remove harmful blobs made by certain enemies and repel incoming projectiles. It also destroys Energy Cells and Life Pads.