This folder holds the skins that are used when sending out emails.
For each email there is one template for HTML emails and one template for Plain-Text emails. More info about email templates.
This folder holds a set of default templates files for each kind of outgoing email. These can be customized. For example
/skins_email/xxx.php can be overridden by
This folder may need to be accessed through the web if some CSS or graphics are used in the custom templates.
A global overview of the codebase can be found here.