MIME stands for “Multimedia Internet Mail Extensions.” MIME was originally invented to solve a similar problem for email attachments.
A MIME type is similar to file extensions but more universally accepted, “MIME types” are used to identify the type of information that a file contains. While the file extension .html is informally understood to mean that the file is an HTML page, there is no requirement that it mean this, and many HTML pages have different file extensions. In the HTTP protocol used by web browsers to talk to web servers, the “file extension” of the URL is not used to determine the type of information that the server will return. Indeed, there may be no file extension at all at the end of the URL.
Instead, the web server specifies the correct MIME type using a Content-type: header when it responds to the web browser’s HTTP request.
Here are some examples of common mime types seen on the web:
Type — Common File Extension — Purpose
text/html — .html — Web Page
image/png — .png — PNG-format image
image/jpeg — .jpeg — JPEG-format image
audio/mpeg — .mp3 — MPEG Audio File
You can find a more thorough list of MIME Types in this article.