SMS stands for Short Message Service, which is commonly known as texting. It is a way to send text-only messages of up to 160 characters between phones. SMS is the protocol that cellular phones use to send and receive text messages over a 2G, 3G, 4G, or 5G network. Unlike app-based messaging services, SMS does not require a data plan to send and receive messages. SMS messages are more simplistic than MMS texts, which support multimedia content. When and if your phone uses SMS messages depends on your cellular carrier, as does the cost of sending one.