
Instant messaging (IM) is a form of real-time direct text-based communication between two or more people using shared clients. The text is conveyed via devices connected over a network such as the Internet.

Instant messaging (IM) is a form of real-time direct text-based communication between two or more people using shared clients. The text is conveyed via devices connected over a network such as the Internet.
IM falls under the umbrella of chat, as it is a real-time text-based networked communication system, but is distinct in that it is based on clients that facilitate connections between specified known users (often using "Buddy List", "Friend List" or "Contact List"), whereas Chat includes web-based applications that allow communication between (often anonymous) users in a multi-user environment. (an analogy would be comparing a telephone and a bar-room. With the telephone, you have to know the contact information to reach the other person, whereas you just show up at the bar and see who is there to chat with)
Instant messaging (IM) is a collection of technologies that create the possibility of real-time text-based communication between two or more participants over the internet or some form of internal network/intranet. It is important to understand that what separates chat and instant messaging from technologies such as e-mail is the perceived synchronicity of the communication by the user - Chat happens in real-time. Some systems allow the sending of messages to people not currently logged on (offline messages), thus removing some of the differences between Instant Messaging and e-mail (often this is done by sending the message to the associated e-mail account).
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