The example in Sample MIME Message shows how MIME uses headers and multiple body parts. But the real power of MIME is in its ability to handle a wide variety of content types. Some encoding schemes are defined by MIME. An even broader range of possibilities is anticipated, and organizational elements are provided to handle the rich set of possibilities inherent in MIME. The "Content-Type:" header field is specified to organize media types. This allows the UA to present the body part to the user in its appropriate form, to engage the services of a tool that can process the body part, or to save the body part as a file for offline processing. The content type can be either "composite" or "discrete."
The two composite top-level media types are:
The five discrete top-level media types are: