It is broadly a communication service component of Global System for Mobile communications (GSM), making use of standard communication protocols that help in the exchanging short text messages between mobile phone devices. In short, it is a mechanism of transmission and delivery of short messages over networks through cell phones.
SMS is a mobile data service, allowing alphanumeric messaging between mobile phones and equipment such as email and voice mail systems. The text message from the sender mobile is stored in a central short message centre (SMSC) and then forwarded to destination mobile. In the absence of the recipient, the message remains in storage for a period of time before sending again. SMS uses signaling channel so that the message can be sent and received simultaneously over the GSM network. As national and international roaming is supported, sending SMS to any other GSM mobile anywhere in the world is possible.