Short Message Service (SMS), or Text Messaging, is the most basic communications technology for mobile data transfer and is characterized by the exchange of short alphanumeric text messages between digital line and mobile devices. SMS messaging's key influential factor is affordability.
SMS messages hold up to 140 bytes (1,120 bits) of data, which allows a 160-character alphanumeric message in the default 7-bit alphabet or a 70-character message in a non-Latin language, such as Chinese.
Source: https://www.techopedia.com/definition/24275/short-message-service--sms