Explanation: When a file is delivered over a network (e.g., via HTTP), the Content-Type header in the HTTP response specifies the type of content being sent. For HTML files, this header is usually:

Content-Type: text/html

The file extension (.html) helps browsers and operating systems identify files locally, but it is not used in network communication. The web server determines how to serve the file based on its configuration and sends the appropriate Content-Type header.