A Web page
The HTML file extension is sometimes abbreviated as .htm for compatibility with older operating systems, such as Disk Operating System (DOS), Windows 3.x and OS/2., which support eight character file names with a three character extension. When you save an HTML document, you can use either the .html or the .htm file extension.
HTML consists of the set of markup symbols or codes inserted in a file intended for display on a World Wide Web browser page. The markup tells the browser how to display a Web page's words and images for the user.
HTM and HTML are the most common type of documents used to build static webpages. Both HTM and HTML may contain links to images, audio, video and scripts.
Any browser or web editing program can open HTM files.
MIME type: text/html
Learn more about HTM files:
Ask your IT peers HTML-related questions or browse HTML FAQ at IT Knowledge Exchange.