Concept where two or more individuals, connected by some form of internet connection, communicate - usually by typing.
Some commonly seen protocols include:
SS: I believed protocols such IRC don't fit well into the instant messaging category. Isn't instant messaging more related to channel-less comunication based on exchange of single messages between two persons? All the protocols involving one-to-more messages are IMHO much more chat systems. Also instant messaging is different from chat protocols because it often can postpone the delivery of messages until the target user is on line, while in protocols like IRC the message exchange is possible only if the users are online at the same time.
So instant messaging seems to me something between a chat and the email service.
Ro: But then again lots and lots of people just log on to IRC and idle, and check for messages every so often. So IRC is something between a chat and the email service.