MMS stands for Multimedia Messaging Service. In SMS (Short Messaging Service) we can send some text message to any other phone (cell phone or land line). The concept of MMS is almost like SMS but in MMS we can send not only the text but also can send the other medias, like sound, video and picture. The multiple medias as involved in MMS, that's why it is called Multimedia Message Service.
The SMS service is provided almost all GSM and AMS networks. But for MMS some additional service also required. This additional service is called GPRS (General Packet Radio Service). By using the GPRS we can browse Internet on our cell phone and MMS is also possible using the GPRS service.
The MMS is also costly than the SMS service. In some countries the MMS rates are almost 5 to 10 time higher than the SMS service. Incoming MMS are also charged by some operators. To use the MMS service the Cell phone should be capable of sending and receiving the MMS message. Older cell phones may lack this facility but almost all the new models have this facility. So we can say the Multimedia Message Service facility is dependent on cell phone, network and GPRS.