isr.co.ro : glossary MIME type/subtype In the Multipurpose Internet Mail Extensions standard used to send nontext data through Internet mail, a two-part stylized description of the message contentused to help the receiving system process the data. Among the types so far registered with the Internet Assigned Numbers Authority include application, audio, image, message, multipart, text, and video. Most of these types have associated subtypes to allow for further variations.