IRC = Internet Relay Chat, it was the precursor to ICQ, MSN, YIM, Skype etc.
It was the first "live" form of internet chat. Originally a stand alone software was needed to connect to servers with lists of chat rooms.
The "chatbox" above the forums is an IRC chat, it's just a newer web based revision,
With access to the server info to log in directly, one would have more power and control of the chat room, especially moderators.