"Texting," as the young whippersnappers call it, was huge in Asia and Europe before it began catching on in the United States. These days, however, it's increasingly popular, especially among teenagers and twentysomethings.
SMS stands for Short Messaging Service. An SMS text message is a very short note (under 160 characters—a sentence or two) that you shoot from one cellphone to another. What's so great about it?
Like a phone call, it's immediate. You get the message off your chest right now.
As with email, the recipient doesn't have to answer immediately. He can reply at his leisure; the message waits for him even when his phone is turned off.
Unlike a phone call, it's nondisruptive. You can send someone a text message without worrying that he's in a movie, in class, in a meeting, or anywhere else where talking and holding a phone up to the head would be frowned upon. (And the other person can answer nondisruptively, too, by sending a text message back.)
You have a written record of the exchange. There's no mistaking what the person meant. (Well, at least not because of voice quality. Whether or not you can understand the texting shorthand culture that's evolved from people using no-keyboard cellphones to type English words—"C U 2morrO," and so on—is another matter entirely.)
All AT&T iPhone accounts include 200 free text messages per month (although you can upgrade your account—meaning pay more—if you send more than that). Keep in mind that you use up one of those ...