NPCs is an acronym used to represent "non-player characters". In Battlestar Galactica Online, NPCs are enemy ships that each faction will encounter in star systems and during missions which are not controlled by another player, but are controlled by the game's internal systems. Examples of the NPCs present in-game are Drones, weapons platforms and opposing faction fighters (either Colonial or Cylon).
Opposing faction fighters are not to be confused with PC (player controlled) fighters. NPCs are displayed as a Rank (ie. Basic, Intermediate, Advanced, Evolved etc) followed by their ship name (Raider, Heavy Raider etc), whereas PC characters are displayed by their character name.