On PvP servers, the zone flagged for the Festival will rotate from place to place, while on the game's dedicated PvE server the festival will take place in the Border Kingdoms to ensure all PvP remains consensual. While in these regions, players can take part in the new Fields of Slaughter events (teams holding a designated region against all comers) as well as the Arena of Death. This comes along with new PvP daily quests, improved PvP gear, bonus experience for alternate advancement, and other rewards. So to celebrate six years of the game, read up on how you can reach out and touch someone. With a pointy bit of metal.
[Thanks to Anders for the tip!]