Text Messaging - also called SMS (Short Message Service) - allows short text messages to be sent and received on a mobile phone.
Messages can be sent from one phone to another by addressing the message to the recipient's phone number.
Messages can also usually be sent to a phone via a special email address, through the carrier's web site, or with special messaging software and a modem.
Most phones and carriers also allow messages to be sent from a phone directly to an e-mail address.
See: Threaded Messaging