MIME discrete media types allow MIME to represent hundreds of different kinds of data in email messages. This alone would make MIME an incredibly useful technology, but the MIME standard goes one step further by defining composite media types. These allow MIME to perform even more spectacular feats, such as sending many types of data at once or encapsulating other messages or information into email.
The use of a MIME composite media type is indicated via the Content-Type header of an RFC 822 message. Instead of one of the six discrete media types (
application), one of these two composite media types is used:
multipart, which allows one ...