All users of the IRC channel are expected to follow the Code Of Conduct
If you have an IRC client that supports the irc:// protocol you can click here to join the channel.
Many of the MusicBrainz developers, as well as other users who want to chat with them, can be found on IRC; references to IRC on the Wiki generally refer to this channel. As in many communities the chatters in the channel have developed their own MusicBrainz Slang. Also, you may want to take a look through IRC Regulars to find out who's who on IRC.
There is a weekly dev chat held every Monday in the #musicbrainz-devel channel that takes about an hour. It usually starts at 8pm UK, 9pm mainland Europe, 3pm EST or noon PST. An invitation is usually sent out to the Developers Mailing List Sunday night/Monday morning.
Internet Relay Chat, IRC for short, is a type of instant messaging network; you will need an IRC client to participate, but even without one, you can browse the IRC logs (there is only an extremely crude chronological index by days, but you can also look at today's log and yesterday's log). For more specific information visit the wikipedia article on Internet Relay Chat.