In addition to regular NPC kills, in Age of Conan they feature Mini-Bosses, Bosses and Raid NPCs. You will come across these "Named" NPCs under various circumstances, such as while clearing a dungeon, as a quest kill and while participating in events and raids. Unless a Boss NPC is intended as part of a solo quest, you will often need a group of two or more players in order to kill one. Raid NPCs may require anywhere from one group to several groups in order to defeat it. Special named Bosses will often drop excellent loot, including coveted gear and weapons. 

Note that any NPC that drops good loot will likely be "contested", meaning that you may find others "camping the mob" to kill it repeatedly for its loot. Camping a Boss NPC is considered poor etiquette, especially if it is a quest NPC.