These are triggeres in the MESSAGING system. As soon as Amazon updates the order status internally we use these to send out your scheudled email.
This is when the order is Seller Central goes from Order Pending to Order Confirmed.
This is when Amazon confirms the order is shipping from their warehouse.
This is based on the date that Amazon estimates your customer will get the order.
If a customer initiates a refund, then emails set up with a ORDER REFUNDED trigger will be sent to them.