In Salesforce Classic, you can create four different types of email templates:
1.Text : In this, All users can create or change text email templates.
2. HTML with letterhead : Admin and users with the “Edit HTML Templates” permission can create HTML email templates based on a letterhead. HTML email templates can inherit the logo, color, and text settings from a letterhead.
3. Custom : Admin and users with the “Edit HTML Templates” permission can create custom HTML email templates without using Classic Letterhead.
4. Visualforce : Admin and developers can create the templates. It allow for advanced merging with a recipient’s data.