IRC - Internet Relay Chat
Internet Relay Chat is the most popular chat system developed way back in 1988 by Jarkko Oikarinen in Finland. The system enables two or more persons to start a live discussion by just connecting their systems to the Internet. Some of the most popular IRC chat programs are mIRC for Windows, Ircle for MAC and ircII for UNIX.
How does IRC works
This real-time text messaging program works on a client-server architecture. The end user needs to install a client software that gets connected to the IRC server available on the Internet. There could be a network of IRC servers connected with each other that helps client systems communicate with each other.
Some latest IRC softwares also allow a user to share file of a specific size and format.