Scenario 1:
All the items were in stock when your order was confirmed, but after your payment was confirmed, one of the items in your order went out of stock
In this case we will ship all the in-stock items that you have ordered first, and products which are out of stock, we will ship it to you immediately once the next shipment of stock arrives.

Scenario 2:
The item was already out of stock, when you made the order
In this case we will ship all items in the order, only when the new stock arrives However, in some situations we might ship the items that are available, first.