A Power Dash, as introduced in the tutorial missions, is where you use Circle to dodge an enemy or to close the gap in distance by dashing forward, or by cancelling your current combo to start up another. You can use this either way, as long as you have the stamina to do so, as characterized by the green wheel that will appear around your character's head once you use it. It will only recharge as you're not performing combos or special abilities, can be immediately refreshed using Full-Force Burst, and can grow in length depending on the number of Stamina upgrades your character has acquired.