From Forum Nokia Wiki

MMS stands for Multimedia Message Service.

The Multimedia Message Service (MMS) is a standard defined by The Open Mobile Alliance (originally by the WAP Forum) for sending and receiving messages with rich content, from user to server to user, over mobile telephony networks.

MMS Characteristics

• MMS operates over dial-up (CSD) or GPRS connections.

• It uses WAP or HTTP for message transports and notifications.

• MMS messages are similar to MIME email messages.

• They contain headers that define the message properties, and a MIME body.

• The format for MMS messages is MIME

 Content-Type: Multipart/Related; 

• The MMS message contains a number of media objects, such as pictures, sounds and text.

• The first object is expected to be a Synchronized Multimedia Language (SMIL) file, an XML document that provides instructions to the client about how to present the other media objects in the message.