This article explains what HTML/HTM files are, how to view them, edit their source code, and how to convert them to different formats such as DOCX, PDF, JPG, etc.
An HTM or HTML file is a Hypertext Markup Language file and is the standard web page file type on the Internet.
Since HTM files are just text files, they only contain text (like what you are reading now) and text references to other external files (like the image in this article).
HTM and HTML files can also reference other files, such as video, CSS, or JS files.