What is IRC?
IRC stands for "Internet Relay Chat". It was originally written by Jarkko Oikarinen in 1988. Since starting in Finland, it has been used in over 60 countries around the world. IRC is a multi-user chat system, where people meet on "channels" (rooms, virtual places, usually with a certain topic of conversation) to talk in groups, or privately. There is no restriction to the number of people that can participate in a given discussion, or the number of channels that can be formed on IRC. To join an IRC discussion, you need an IRC client and Internet access.
Some IRC Clients:
mIRC - popular Windows graphical client
XChat - popular Linux/Windows graphical client
XChat Aqua - popular Mac OS X port of XChat
BitchX - popular terminal based client for Unix-like operating systems
Irssi - popular terminal based client originally for Linux but now for Windows also