The description of htm format expansion
The htm file is an HTML web-page, used by the web-browsers. Contains the markup code, which is stored as a plain text. Applied in order to display and format text and images in the web-browser.
The htm-files serve to the same purpose, as the htmL-files. The “htm” extension first appeared in times of Microsoft web-development programs usage, such as Expression Web, SharePoint Designer and FrontPage.
The HTM-file can be encountered much rarer, then HTML-files.