Dash by double-tapping the movement key, becoming invulnerable and damaging enemies. There's a short cooldown before Isaac can dash again.
Quote
"Double tap dash"
Effects
Double tapping a direction makes Isaac quickly dash in that direction.
Isaac is immune to damage from all sources during the dash, with the exception of Blood Donation Machines, Devil Beggars, and similar self-damage active items.
The dash deals damage equal to 4x Isaac's damage + 8.
The direction of the dash can be changed by holding another button.