What is iMessage?

iMessage is Apple’s app that operates like a cross between traditional text messages and more modern instant messaging software like Google Chat.

 
First released in iOS 5, the name Apple uses for its mobile operating system, iMessage is automatically installed on any iPhones, iPods or iPads that can run that version of the software or newer.
 
Text messages and more
 
Replacing what used to be the Messages app, iMessage allows you to send unlimited text messages, photos, contacts or locations to anyone else you know who also owns one of Apple’s mobile devices. 
 
You can still send use iMessage to contact friends and family who don’t own an Apple device, but it will cost the usual mobile phone network operator’s fee for sending a message.
 
As well as standard functionality like group messaging, delivery reports and read receipts, which let you know when your message has been read, iMessage also operates like an instant messaging service by allowing you to see when your friends are typing you a message.
 
Another key feature is that you can start a conversation on one of your Apple devices, say an iPhone, and pick it up on any other devices you have running iOS 5, such as your iPad.