1) A short message is a brief text message sent to or from a mobile phone subscriber through the Short Message Service (SMS). The standard short message consists of up to 160 alphanumeric characters, although messages at least 50% longer can be sent using data compression. Developed as part of the Global System for Mobile communications (GSM) Phase 1 standard, a short message is exchanged between two mobile devices or between a nonmobile device and a mobile device (for example, a short message can be sent from a PC attached to the Internet to a mobile subscriber). Short messages are stored in and forwarded from a Short Message Service Center (SMSC) so that - unlike the user of a pager - the recipient can get messages that arrive when their mobile device is not turned on.
SMS compression increases the amount of text that can be sent, and SMS concatenation enables short messages to be strung together into a longer one. Users of devices that are not SMS-enabled can send short messages using an alternate version known as Internet SMS.
2) Instant messaging (IM) messages are also sometimes referred to as short messages. To make the most of a short message, people frequently use a shorthand typing mixture of letters and numerals known as Alphanumerish.