It's an extension of the basic SMS (Short Message Service) that allows for sending and receiving messages with rich content. 

• Rich Media Content: Unlike SMS, which is limited to text, MMS allows users to send and receive rich media, including images, audio files, short videos, and text messages longer than the standard SMS character limit.

• Compatibility with Mobile Devices: Most modern mobile phones and smartphones support MMS, enabling users to send multimedia content without the need for additional apps or services.

• Use of Data Networks: MMS messages are transmitted over cellular data networks, as opposed to the voice network used for SMS, which means that an active data plan is usually required to send and receive MMS messages.

• Integration with SMS: MMS is integrated with the existing SMS infrastructure, allowing a seamless user experience. If a phone cannot receive MMS messages, the message may be delivered as an SMS with a link to view the content online.

MMS has significantly expanded the capabilities of standard text messaging, allowing for a richer and more engaging communication experience on mobile devices.