Magento Open Source, 1.9.x
Email Template Setup

Email templates contain the content and formatting for automated messages that area sent from your store. These messages are called transactional emailsAn automated email message that is sent in response to a specific event or transaction. because each one is associated with a specific type of transaction or event.

Your store has a set of default templates that you can customize. After creating a customized version of a template, remember to update your system configuration so the correct template is used for the message.

Sales Email Configuration