Role-Players put themselves in the role of player characters characters adventuring in the Star Army universe. Quite simply, a player character (PC) is a character that any player primarily controls in any sort of game setting. Usually, these are the characters you spend the most time developing in a roleplay setting because they are the ones that the story will revolve around.
Characters not played by role-players are Non-Player Characters (NPCs); NPCs are controlled by a plot's Game Master.