Online chat may refer to any kind of communication over the Internet that offers a real-time transmission of text messages from sender to receiver.
Online chat in a less stringent definition may be primarily any direct text-based or video-based (webcams), one-on-one chat or one-to-many group chat (formally also known as synchronous conferencing), using tools such as instant messengers, Internet Relay Chat (IRC), talkers and possibly MUDs.
The expression online chat comes from the word chat which means "informal conversation".
Online chat includes web-based applications that allow communication – often directly addressed, but anonymous between users in a multi-user environment.
Web conferencing is a more specific online service, that is often sold as a service, hosted on a web server controlled by the vendor.
The first online chat system was called Talkomatic, created by Doug Brown and David R.
Woolley in 1973 on the PLATO System at the University of Illinois.It offered several channels, each of which could accommodate up to five people, with messages appearing on all users' screens character-by-character as they were typed.Talkomatic was very popular among PLATO users into the mid-1980s.In 2014, Brown and Woolley released a web-based version of Talkomatic.The first online system to use the actual command "chat" was created for The Source in 1979 by Tom Walker and Fritz Thane of Dialcom, Inc.The first transatlantic Internet chat took place between Oulu, Finland and Corvallis, Oregon in February of 1989.