When creating Order Follow Up emails through Privy, for Shopify Plus, Shopify and Bigcommerce stores, you can easily add an order summary to your email to summarize the items purchased.
By entering into the Email Content editor, you will see the "Order" placeholder that can be dragged and dropped into the place you would like the order summary to appear.
The order summary will look like a placeholder in the editor, but will appear in an itemized list when sent to someone post-purchase. By sending yourself a test email with this placeholder, you can see example items to give reference.
See the linked article for more information about Order Follow Up Emails.