A life of consequence, Emergent AI as seen in the SOE Live 2013 panel of EQN

Emergent AI is a game feature in EverQuest Next

The AI in the game remember everything you did, and NPCs will behave differently based on your past actions.

NPCs, Quest Opportunities, etc, will be different based on what you have done.

Enemies will also think where to camp and not just spawn randomly

Foe example, Orcs will go and ambush locations that are far from cities, and in which not many players have passed near it recently. If more players come to the location to repel the orcs away, the orcs will find a different location to camp.

The adventurers (players) can also report the Orcs to the guards in which case the guards will start patrolling the roads, forcing the Orcs to leave and find a different place. Or the Orcs could be pissed off and could band and try to push back at you.