MusicBrainz uses two IRC channels for real-time chat and discussions. For more information about IRC in general, see the Wikipedia article. If you don't have an IRC client (such as mIRC or Colloquy), Freenode provides a web-based client.
Please note that all users of the IRC channels are expected to follow the Code Of Conduct.
The MusicBrainz community and support channel is #musicbrainz on irc.freenode.net
Among the regulars in this channel are quite a few of the developers as well as some of the auto-editors and other active MusicBrainz users. Anything related to MusicBrainz, including Picard and other MusicBrainz products, is welcome here. References to IRC in MusicBrainz generally refer to this channel. As in many communities, the regulars in the channel have their own slang.
The development and general MetaBrainz channel is #metabrainz on irc.freenode.net
Apart from MusicBrainz development, this channel also hosts general MetaBrainz talk, incl. discussion about all the other *Brainz projects: BookBrainz, CritiqueBrainz, AcousticBrainz, ListenBrainz, MessyBrainz, and the Cover Art Archive. There is a weekly dev chat held in this channel. A reminder is normally sent out to the developers mailing list Sunday night/Monday morning.
There are also channels in other languages than English:
BrainzBot is a bot which logs all conversion in the MetaBrainz IRC channels. You can see all of the chat log archives at http://chatlogs.metabrainz.org/. BrainzBot will not log messages that start with "[off]", so feel free to use that if you have some sensitive messages.