%20-%20added%20variables%20when%20editing%20created%20template.png?version=1&modificationDate=1526043762198&cacheVersion=1&api=v2 "Email Task > Template Variables [2.4.x] > Send Email Dialog (2.4.x) - added variables when editing created template.png")
In an mail template body (3) and subject (2) you can insert special tags called template variables:
In case of an email subject, you must type it manually or copy the variable string from the email's content.
They are dependent of an issue (1↑) for which an user wants to render template. Template Variables come from available fields from selected issue type (so e.g. sub-task issue type may not have all of the variables present in a task issue type)
When you insert variable i.e. ${issue.key} into the body's content, then Email Task will replace this value during sending en email from a specific issue. You can always preview your template variables added on subject and email body on your mail template in preview dialog for selected issue.