The below mentioned are the list of templates available in Salesforce :
Text Template: This template can be modified or changed by any user.
HTML with letterhead: People like administrators and users with Edit HTML permission can create this email template based on letterhead.
Custom HTML: People like administrators and users with Edit HTML permission can create this email template without using letterhead. It requires knowledge of HTML or gets the HTML code to insert it into the email template.
Visualforce Email Template: This template can only be created by administrators and developers using VisualForce. It is capable of merging the data from various records.