There are two primary ways that customers can be notified of the order status when things happen:
- Automatic emails that are triggered by activity
- Manual emails that are sent by the merchant (you)
Customers will automatically receive notifications when the order is placed and when the line items are shipped. Those are Order New Receipt and Order Shipment. If you perform split shipments, there will be emails sent for each shipment.
Manual emails can also be sent at any point of the order workflow process by any authorized user. Some common scenarios might include notification due to order notes being added, or payment being processed.
You can do this by simply selecting the email template and clicking a button while looking at the order details.
There are numerous use cases that we don't know about that are specific to the needs of individual stores, where you would want to send emails in an automated way. If this is the case for you, you can use a custom order workflow task to send the email. It will require a developer to implement, but here's a code sample to help you.