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IRC stands for Internet Relay Chat and it is a text chat system where you can talk to community members in the channel #cryptoparty on the irc.oftc.net server.
You can use one of many dedicated IRC clients (such as pidgin, which you might already know from Jabber+OTR) or OFTCs browser client (which can also be used with the Tor Browser Bundle).
For advanced use, see the irssi+tor guide and the Torprojects Torify HowTo (irssi).