SMS

Short Message Service (SMS): The universal, 160-character text protocol for reliable, asynchronous communication across all cellular networks.

SMS (Short Message Service) is the foundational text-messaging component of mobile systems, standardized under the Global System for Mobile Communications (GSM) protocol. Its defining technical specification is the 160-character limit (using GSM-7 encoding), transmitted over the cellular signaling channels. The first commercial message was sent in December 1992; today, the technology remains critical for application-to-person (A2P) messaging, including two-factor authentication (2FA) codes and high-priority customer alerts, boasting superior delivery rates compared to email.

https://www.gsma.com/aboutus/technology/gsm