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.
Enemies are AI-controlled monsters and other hostile creatures that players can battle.