IRC

Short for Internet Relay Chat, a chat system developed by
Jarkko Oikarinen in Finland in the late 1980s. IRC has become
very popular as more people get connected to the Internet
because it enables people connected anywhere on the Internet
to join in live discussions. Unlike older chat systems,
IRC is not limited to just two participants.
To join an IRC discussion, you need an IRC client and Internet access.
The IRC client is a program that runs on your computer and sends
and receives messages to and from an IRC server. The IRC server,
in turn, is responsible for making sure that all messages are
broadcast to everyone participating in a discussion.
There can be many discussions going on at once;
each one is assigned a unique channel.