I'm starting a new campaign in which I'll be teaching a few newbies how to play, and it's got me thinking about how to define what exactly a "PC" is. Not as far as the rules or concerned, that's pretty cut-and-dried, but where PCs fit into the world. How you think of the PCs frames how the players interact with the game world. Below is the broad spectrum I came up with:

• Heroes: The PCs are exemplars, defending the weak and fighting the forces of evil. Even when the pay isn't great and odds of survival look bleak, the PCs forge onward knowing, in their hearts, that what they do is for the greater good, and that they will live on as the stuff of legend.
• Adventurers: The PCs fend off evil's grasp on society, if only to keep their favorite tavern in business. But, truly, they live for the feeling of exhilaration in a pitched combat or upon uncovering an ancient artifact. They might be in it for the money, but most likely that's just a secondary benefit to exploration and overcoming dangerous obstacles.
• Mercenaries: The PCs gotta eat too. If they're going to go through the trouble of fighting off yet another goblin war-chief or descending into a dungeon known to be cursed, you better believe they want to get paid for it, preferably in advance. They still have holdouts about working for the forces of evil... But they think about it.
• Outlaws: The PCs are in it for either the gold, the power, or both. Even in situations where their desires are fulfilled without necessitating any law-breaking, they still often grate on local law enforcement. Things only get worse when the bad guys have more to offer. Still, if things ever went sour, they'd turn on their would-be masters; who knows, maybe that pesky constable will offer a reward.
• Villains: The PCs are the forces of evil. Gold and power are merely tools with which existing societies can be torn down and rebuilt in PCs' image. Even other PCs are little more than very powerful tools, but sometimes tools lose their utility.