Non Playable Characters (NPCs) are characters that are not controlled by any player. They often interact with the player in some way, be it selling items or in doing quests. In Final Fantasy Epic RPG, NPCs that have a quest available have a yellow exlcamation point (!) over their heads. If you are currently on a quest for an NPC, they will instead of a grey question mark (?) over their heads.
Additionally, some NPCs have a small bubble with a red exlamation point (!). Approaching one of these NPCs will make them tell you something. Often, what they say is miscellaneous information about their area, but is sometimes a hint to hidden game content.