SMS, MMS, and iMessage
SMS stands for short messaging service, but it is commonly referred to as text messaging. Text messages are a great way to quickly touch base with people without interrupting them with a voice call. Sometimes you can text people and receive a text reply when it would be impossible or difficult to do a voice call.
MMS is short for multimedia messaging service, which provides a quick, standard way to send pictures, video, voice memos, map locations, and contact cards.
iMessage is Apple's new service that does exactly the same thing as SMS and MMS, but works over your data plan and only with other iOS 5 devices. ...