MIME types, or Multipurpose Internet Mail Extensions, are a way to specify the nature of a file on the internet. They help web browsers and servers understand how to handle different types of content, such as text, images, or videos. For example, a file with a MIME type of image/jpeg indicates that it is a JPEG image, while text/html signifies an HTML document. When a web server sends a file, it includes the corresponding MIME type in the HTTP headers. This allows the browser to display the content correctly or prompt the user to download it. Proper use of MIME types ensures a smooth user experience on the web.