NPCs or Non-Player Characters are any characters not controlled by players. NPCs are divided into 2 types, friendly and hostile. Friendly NPCs include quest-givers that assign quests and vendors that sell items. Hostile NPCs are enemies controlled by A.I. that players can battle.
These NPCs are involved in quests. Some of these NPCs are quest starters while others are involved in quest steps.
Guildleve NPCs or Levemetes are NPCs that assign various Guildleves such as Battlecraft Leves, Tradecraft Leves, Fieldcraft Leves and Grand Company Leves.
Vendor NPCs sell various items to the players. Some items might not be available for sale until the player has completed certain quests or reached specific reputation ranks.
Enemies are AI-controlled monsters and other hostile creatures that players can battle.