SMS - Short Message Service
Short Message Service is a communications protocol that allows to exchange text messages between mobile devices. It cab be sent from mobile phones, smart phones, handheld devices, web and even landlines telephones. All the major service providers in India, including : Airtel, BSNL, Reliance, Idea and many more, provides the facility of sending SMS.
SMS was originally designed as part of GSM, but is now available on a CDMA phones, including 3G networks. The maximum individual message must be no longer than 160 alpha-numeric 7-bits characters (224 characters are possible if using a 5-bit mode).