Short Message Service (SMS) is a text messaging service component of phone, Web, or mobile communication systems. It uses standardized communications protocols to allow fixed line or mobile phone devices to exchange short text messages.
SMS was the most widely used data application, with an estimated 3.5 billion active users, or about 80% of all mobile phone subscribers at the end of 2010. The term "SMS" is used for both the user activity and all types of short text messaging in many parts of the world. SMS is also employed in direct marketing, known as SMS marketing. As of September 2014, global SMS messaging business is said to be worth over USD 100 billion, and SMS accounts for almost 50 percent of all the revenue generated by mobile messaging.
SMS as used on modern handsets originated from radio telegraphy in radio memo pagers using standardized phone protocols. These were defined in 1985 as part of the Global System for Mobile Communications (GSM) series of standardsas a means of sending messages of up to 160 characters to and from GSM mobile handsets.Though most SMS messages are mobile-to-mobile text messages, support for the service has expanded to include other mobile technologies, such as ANSI CDMA networks and Digital AMPS, as well as satellite and landline networks.
(Source: Wikipedia)