Instant Messaging (IM) is a form of real-time communication between two or more people based on typed text. The text is conveyed via computers connected over a network such as the Internet.
Instant messaging (IM) and chat are technologies that facilitate near real-time text-based communication between two or more participants over a network. 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 before your eyes. Some systems allow the sending of messages to people not currently logged on (offline messages), thus removing much of the difference between Instant Messaging and e-mail.
While many IM services have additional features such as: the immediate receipt of acknowledgment or reply, group chatting, conference services (including voice and video), conversation logging and file transfer, those functions are beyond the scope of this article.
IM allows effective and efficient communication, featuring immediate receipt of acknowledgment or reply. In certain cases Instant Messaging involves additional features, which make it even more popular, i.e. to see the other party, e.g. by using web-cams, or to talk directly for free over the Internet.
It is possible to save a conversation for later reference. Instant messages are typically logged in a local message history which closes the gap to the persistent nature of e-mails and facilitates quick exchange of information like URLs or document snippets (which can be unwieldy when communicated via telephone).