An order is unconfirmed if it is placed but there is some issue with the payment. 

For example, if you place an order worth Rs. 280 and you have Rs. 100 as credits. The merchant panel takes you to the payment gateway to make the pending payment.

If by mistake the browser closes, or the internet is disconnected or you press cancel, the order is saved as an unconfirmed order.

If the payment transaction fails, the spent credits are refunded.

If the payment gateway is disconnected, the credits are saved and can be manually refunded using the Unconfirmed Orders section.