If your plug-in uses binary data that is not an image, audio, or video, this one's for you. The message type is used to encapsulate a mail message. Again, this is not of much use for plug-ins. The image type handles still image or picture data in many different formats. This type plays an important role in displaying graphics on a Web browser.
Some examples are jpeg , gif , and tiff .
The audio type handles audio data, usually in PCM format. Approved audio subtypes are basic and 32kadpcm . The video type is used for transmitting video data. This video data can contain interleaved audio, depending on the video file format. The Content-Type header field is most important because it contains the MIME type and subtype.