IRC is the technology Travian Games uses for the chat systems outside the game.
IRC stands for Internet Relay Chat and is actually older then the web itself. More information about this can be found here.
Begin March 2006 Travian Games created its own dedicated IRC Network and currently over 1000 users are connected at any time during the day.
Most countries have created their own channel on the network which can normally be found by using the chat option in the menu or joining the channel #travian.XX. XX being the TLD of your country.
Example for www.travian.com – #travian.com