Internet Media Types
Formerly known as MIME (Multipurpose Internet Mail Extension) types. These identify different types of files allowing software to handle them correctly. Puppy uses the standard provided by freedesktop.org.
When making a non-standard MIME-type use x- in the MIME-type name, for example application/x-tmd for a TextMaker document (registered ones are at www.iana.org/assignments/media-types/ IANA.org assigned media-types).
Also see
SharedMimeInfo shared-mime-info - MIME-Type descriptions from freedekstop.org