The most-read messages your shop sends.
WHERE TO CONFIGURE
WooCommerce > Settings > Emails. Each email type can be enabled, and its subject and heading edited.
Set the From name and From address at the bottom. Use an address on your own domain, never a Gmail address, or the emails will fail authentication.
THE IMPORTANT ONES
New order, sent to you Processing order, sent to the customer when payment clears Completed order, sent when you dispatch Refunded order Customer invoice, which you can send manually
MAKING SURE THEY ARRIVE
This is the part shops get wrong. WooCommerce sends through WordPress, which by default uses PHP mail and is frequently filtered as spam.
Install an SMTP plugin and send through a mailbox on your domain. Then confirm SPF and DKIM are correct in cPanel > Email Deliverability.
An order confirmation that lands in spam produces a support message and an anxious customer.
TESTING
Place a test order and confirm every email arrives, at Gmail as well as your own domain.