HFS: MIME Types
What is a MIME type?
A MIME type is effectively information describing the kind of document retrieved from the web server. Since a web server can furnish many types of documents, the browser needs a way to know the specific document type in order to display it properly.
Is not the file extension enough?
Sometimes file extension is not enough. For example, In the web environment, when a PHP script generates a jpeg image, you get an URL with a .php extension. However, the browser knows that the content represents a jpeg image because it gets this information in the http header as a MIME type.