Elite NPC's are a special, different type of NPCs that do more damage and have more health than usual. You know that the NPC you are fighting is elite if they have two silver arrows next to their name. An enhanced type of elite has 2 gold arrows next to the NPC's name, giving it a much larger amount of health and attack power than a non-elite form of the opponent. These are often referred to as "Boss" or "Gold" elites.
As of Chapter 6, all Elite and Gold Elite NPCs have been enhanced. The update added a claw surrounding all elite's Combat level number.
This is probably because SOE wanted more group efforts and were annoyed with how easy it was to do quests that had elite NPCs