Files with .DOT extension are template files created by Microsoft Word to have pre-formatted settings for generation of further DOC or DOCX files. A template file is created in order to have specific user settings that should be applied to subsequent files created from these. These settings include page margins, borders, headers, footers, and other page settings. Such templates are used in official documents such as company letterheads and standardized forms.
Files with .htm extension represent Hypertext Markup Language for creating web pages for display in web browsers such as Google Chrome, Internet Explorer, Firefox, and a number of others.