In your store's Admin area, go Go to the Sales > Orders > → Orders → Edit Order
These are used for storing Save some additional order details, such as payment results, and for adding add notes to the order for customers to view. Some payment gateways also add notes for debugging.
In the Status & Comments area page the store owner can change the status of an order, type a new comment to the customer to read when logged into their store account, and by checking the "Notify Customer" and "Append Comments" checkboxes the customer is notified via email and a new comment is added for tracking.
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