Administrators can copy an existing template to create a version that inherits its properties (except permissions), which you can then edit while retaining the original. You should always copy a Default System template if you want to change it because whenever the LMS is upgraded to a new version the System Default templates are reset, so any changes made to them are lost. When you copy a template the new copy is saved as a User Template.
To copy an email template
Additional Information
Add a Language to an Email Template