The Short Message Service (SMS), as defined within the GSM digital mobile phone standard that is popular in Europe, the Middle East, Asia, Africa and some parts of North America, has several unique features:

A single SMS can be up to 160 characters of text in length. Those 160 characters can comprise of words or numbers or an alphanumeric combination. Non-text based SMS' (for example, in binary format) are also supported.

SMS is a store and forward service, in other words, SMS' are not sent directly from sender to recipient, but always via an SMS Center instead. Each mobile telephone network that supports SMS has one or more messaging centers to handle and manage the short messages.

SMS features confirmation of message delivery. This means that unlike paging, users do not simply send an SMS and trust and hope that it gets delivered. Instead the sender of the short message can receive a return message back notifying them whether the SMS has been delivered or not.

SMS' can be sent and received simultaneously with GSM voice, Data and Fax calls. This is possible because whereas voice, Data and Fax calls take over a dedicated radio channel for the duration of the call, short messages travel over and above the radio channel using the signaling path. As such, users of SMS rarely if ever get a busy or engaged signal as they can do during peak network usage times.

Ways of sending multiple SMS' are available. SMS concatenation (stringing several short messages together) and SMS compression (getting more than 160 characters of information within a single short message) have been defined and incorporated in the GSM SMS standards.