Events are persistent area cooperative 'quests' which occur as a consequence of players interacting and exploring the world system. If players do not kill monsters in an area, for instance, the mobs may get strong enough to take a fort, which could then be taken back by players. A player might find a caravan on their travels which needs defending. Succeeding or failing at an event could have flow on effects causing other events to happen in the world, and as such the events are not tied to a time schedule.
Events are designed to replace traditional RPG/MMO quests, to the extent that "you won't see a single exclamation mark floating above a character's head in Guild Wars 2." Each event will be communicated to players in the zone so they can participate. Events are intended to prevent spawn camping and kill stealing of major objectives prevalent in other MMORPG by allowing any interested players to cooperate towards an objective and each be rewarded for their participation.
The event system is built around regular events and unusual easter egg events. The intent is that at any one time, you cannot know exactly what state the world is in and what you might see wandering around.
Three examples have been provided to illustrate how this system may work.
The first example shows the arrival of a dragon near a particular town or village. The players nearby that town or village can choose to fight the dragon. If they are successful, the dragon may flee or die, and the players involved are rewarded by the village elder; if the players fail, the dragon destroys a bridge vital to the village. At that time, the village people attempt to build a new bridge, and the players may help them by fending off a group of bandits that see the opportunity to attack.
In the second example, if a player happens to be inside a garrison when a scouting party returns, they may overhear the scouts warning of an approaching column of centaurs, intent on destroying the garrison. The players can then participate in defending the garrison from the attacking centaurs. If the players are successful, the garrison may ask them to participate in a counterattack. If they are not successful, or if they weren't at the garrison in time to save the garrison, they may join other soldiers from a nearby town attempting to recapture the garrison.
The third example involves a player walking along a familiar road, but this time they happen upon a caravan traveling along the road. They can choose to travel with the caravan, and defend it from roving bandits, or not.