A mobile receiving a text message.

An SMS, or short messaging service is a type of communication used in mobile phones. They are more commonly called 'text messages'. With SMS, someone can send text to another person.

SMS can be slow, as a network gives priority to phone calls, and only carries text messages after calls are handled. There is also a limit of 160 characters that a text message can send. Longer messages than this will be sent as multiple messages, where the sender has to pay for each individual message.