Store Credit is cash in your account which you can use towards your future purchases. It will automatically apply at checkout whenever you place an order.
You get Store Credit when you return an item of an order that includes several items and that you've paid using VIP Member Credits. As we cannot refund you for a full VIP Member Credit because the refunded amount is lower than a credit value, we add Store Credit to your account instead.
You can always check your Store Credit balance in your account homepage.