Whenever you send a text message from your mobile phone it goes through a network provided by your cellular network of choice. Virtually all of the major wireless networks in North America have some sort of message center, which routes text messages to make sure they make it from sender to receiver.

SMS messages are by definition very short (under 160 characters), meaning that they use up very little bandwidth when compared with regular voice calls.

The SMS text messaging format was originally designed for use with GSM (Global System for Mobile) networks, but has since been extended to more advanced wireless technologies, including high-speed 3G networks.