Invoice template
Invoice template is a feature that allow you to customize your own template by editing directly the code in admin or in file.
INFO
You can see this feature in Admin -> Ecommerce -> Invoice template.
Template uses Twig template so it's very secure.
There are available some variable that you can use them.
If you want to edit directly in source code file, then go to platform/plugins/ecommerce/resources/templates/invoice.tpl.