If I move a unit with Irresistible Faefolk, is that enemy unit attacking or defending?

When you use Irresistible Faefolk to move an enemy unit to the battlefield it just entered, the enemy unit becomes the defender.

According to RiftJudge FAQ #9581 and #9423, the determination of attacker and defender is based on who applied the "Contested" status to the battlefield first:

1. You are the attacker: When you move Irresistible Faefolk to an uncontrolled battlefield, you are the player who applies the "Contested" status. This makes you the attacker (Rule 459.2.b.1).
2. The enemy is the defender: When you subsequently use the ability to move an enemy unit to that same battlefield, that unit joins the combat as the defender.

Even though your ability moved the enemy unit, you remain the attacker because you were the one who initiated the combat by applying the "Contested" status to the battlefield first.