Internet Relay Chat (IRC) is a system that facilitates transfer of messages in the form of text. The chat process works on a client/server model of networking. IRC clients are computer programs that a user can install on their system. These clients are able to communicate with chat servers to transfer messages to other clients. It is mainly designed for group communication in discussion forums, called channels, but also allows one-to-one communication via private message as well as chat and data transfer, including file sharing. .
Source : Wikipedia
A quite complete tutorial is available here: http://khaganat.net/wikhan/en:irc.
To connect directly, without searching much, just go on http://webchat.freenode.net/?channels=ryzomforge. Enter the user name you want to use in “nickname”, for example your IG character name. “channel” is simply ”#ryzomforge”, already filled in. You can choose another channel name if you want. Copy the captcha (numbers or text in the images) without error and click on “Connect !”
You'll join Ryzom Forge channel.
Once connected, you can enter /join #nomducanal to join other channels.
Ryzom is using the Freenode network. The various channels are: