Phone on left with iMessage blue message bubbles, on right with SMS green message bubbles.
Facetime between most Apple devices with a forward-facing or FaceTime camera
Messages is an instant messaging app developed by Apple for OS X and iOS operating systems. It also supports SMS on the iPhone.
Messages supports iMessage which allows users to send unlimited messages, photos, videos, contacts, and documents to any Mac, iPhone, iPad, iPod Touch running iOS 5 or later. Messaging is allowed between individuals or groups. Users may set up read receipts to see when a message has been read and users of the service can see when the other person is typing a message.
Messages uses SMS to send texts to users on non-iOS devices. On Apple devices, SMS based messages are colored green and iMessage messages are colored blue.
Make video calls between most Apple Devices with a forward-facing or a FaceTime camera: Macs, iPads, iPhones (iPhone 4 or newer), or iPod Touch, or any combination of these devices. FaceTime currently does not work with non-Apple devices or other video chatting software like Skype.