NPC stands for Non-Player Character. There are several dozen in the world of Cabal, distinguishable by green text above their heads.
There are basically 2 types of NPCs.
These NPCs have a specific function. For example, the Officer is specialised in Guilds and the Instructor is specialised in Skills. Their locations are shown on the Map(short cut key M)and follows the legend given at the left side of the pop up.
Some NPCs in towns may be non-interactive. Such as Bodyguard Hurdor and Bodyguard Hursurf in Bloody Ice. While others in towns may not have specific functions, they are often delegated with a quest for players.