The wording and look of the emails the system sends by itself: order confirmations, invitations, password resets and the like.
Each language is its own version
A template is an independent version per language. Editing the Persian one does not touch the English one.
The language chosen when sending comes from the email itself — from the site it relates to — not from the one you have open on this page.
An untranslated version is not sent blank
If you have not written a version for a language, the email does not go out empty; it falls back to the English one — not to whichever other language happens to exist.
So leaving a language unwritten does not break sending, but the recipient reads it in English. For any language other than English and Persian, that is what happens until you write a version yourself.
A site's template sits on top of the platform's
Each template has a default version for the whole installation, and the active site can have its own. Write one for a site and only that site uses it.
Variables cannot be invented
Each template has an explicit list of permitted variables, shown beside the editor. Anything not on that list is not substituted and is shown to the recipient literally.
The template does not build the whole look
The colours, the header and the footer come from the system's own visual identity and from the sending site's brand. What you write here is the content inside that frame.
So there is no need to rebuild the appearance in every template — and if the site's branding changes, every template follows it.
The preview is what gets sent
The preview beside the editor is built by the same engine that builds the real email, with sample values in place of the variables.