SMS stands for Short Message Service and is another name for a text message. SMS is the only standard with the ability to send text messages to (almost) any mobile phone over telecommunications networks.
A single SMS is limited to 160 characters, however most modern mobile phones are capable of segmenting and re-assembling messages up to 1,600 characters. This limit is for messages encoded in 7-bit GSM-7 encoding; see our complete discussion on SMS Character Limits here.
The limit was originally set because SMS was designed to fit in between existing phone protocols. After it took off, the limit was then enshrined in the SMPP Protocol. SMPP is how text messages are transmitted between carriers.
Natively SMS can't handle pictures, videos, or attachments. To serve those purposes, in 1999 the MMS standard was ratified. MMS stands for Multimedia Messaging Service which enables people to send pictures, videos, and attachments over text messaging channels.
Once the multimedia is received by the destination carrier the carrier sends a SMS asking the phone to download the content.
The standard for SMS was agreed in 1984 and the first Nokia phone to support SMS was the Nokia 1011 introduced in November 1992. The first Nokia phone to support MMS was the Nokia 7650 released in June 2002.
The reason SMS text messages have remained so popular is because only SMS can reach almost all mobile phones. All modern non-SMS messaging either requires a particular operating system or application to be installed for both sender and recipient. The most notable phone based messaging product that remains is iMessage (iOS and Mac only).
SMS remains one of the best ways to communicate with people on mobile phones, boasting a 5x open rate when compared to email. Very few of the messaging apps have open APIs, so SMS is one of the only ways to reliably reach someone on their phone via software.