When an Order is first created, it has an empty ShippingGroup, which serves as the default Shipping Group for the Order and also an empty Payment Group which serves as the default Payment Group for the Order. The type of default groups that are created is determined by the defaultShippingGroupType & defaultPaymentGroupType property of the OrderTools component.
By default, defaultShippingGroupType property is set to hardgoodShippingGroup in and defaultPaymentGroupType property is set to creditCard in ATG Consumer Commerce.
Before the Order is checked out, all of the order’s commerce items must be a part a ShippingGroup. This requirement is checked during the checkout process by the validateForCheckout pipeline, which is executed by the processOrder pipeline.