Fluff (or Lore if you want to be more polite and less demeaning) is gamer slang for the histories and colorful descriptions used for a game or game setting that have no mechanical effect on the game's rules. It is the opposite of Crunch.
Powergamers will ignore fluff to focus on the crunch of target numbers, dice pools and maximum efficiency. Their counterparts, roleplayers, will design characters or units based solely on the background stories behind choices to the point where the actual characters or units are functionally worthless. Fluffy characters are interesting, fluffy armies are intriguing, fluffy mecha are intricate ... and all of them will go down like a senior citizen with a wet-cardboard walker the first time they get involved in a conflict because they fail to take into account that a roleplaying game is still a game that can be lost if you don't pay enough attention to the rules.
So, who cares about fluff? Stop for a minute, and look around you. Do you have ANY IDEA how many articles on this wiki are dedicated just to talking about Warhammer and WH40K fluff? DO YOU? It makes a grown man weep.
Sometimes fluff will experience an apotheosis, and ascend into crunchhood. The elegan/tg/entlemen have a knack for doing this. The textbook example would be the Angry Marines, who started as a single funny picture, turned into a running gag, and then by the magic of "/tg/ gets shit done," turned into a full Space Marines chapter with a published codex.
Roleplayers take their fluff seriously, even when it has no effect on gameplay what-so-ever. If it isn't grimdark enough, or noblebright enough, or manly enough, or weeaboo enough, or subtle enough, they throw bitchfits, even if the game's mechanics are perfectly sound and can be played well enough on their own. You can find them scurrying up and down official and unofficial forums like roaches, gnawing on the ankles of wiki articles, desperately trying to find an outlet for their rage. The air will reek of Skub. Then again, the only thing separating Magic: The Gathering from Poker, and Warhammer 40k from Chess, is the fluff. Even games that don't appear to have Fluff at all, such as Risk, uses the benefit of Historical or fantasy settings to differentiate it from a game that simply involves rolling a dice and having more tokens on your side. Though admittedly, those latter games are also addicting, but the moment you turn your pawn into a Imperial Guardsman, something more than mechanics would be at work there.
Fluff can make or break a faction, or even an entire game. A sub-optimal force of units in a skirmish game can rake in a huge fanbase if the fluff is appealing. On the other hand, an efficient and effective army force is shunned because of the horrible, Mary Sue saturated fluff of its faction history. (Insert your own Matt Ward reference here, it hurts too much to write about it.) The Fluff creates breadth and depth in a game that would otherwise be utterly 2D with cardboard cut-outs of blandness. In an extreme tangent, it is the Fluff that helps to prevents you from seeing your brave fighting men and women as mere deductible numbers on a list.
"Narrative" game systems try to get the best of both worlds by turning character background and personality into mechanical features that can be called upon during conflict. The cleanest example of this would be the FATE system, where characters write down 2-10 "aspects" (very specific descriptions or catchphrases) for events in the character's background history. Even locations can have "aspects" from the history of events at that place. These "aspects" can be invoked during conflict for either a bonus to a die roll or to get a re-roll. Another game that tries to integrate fluff into play is Mouse Guard with its sequence of Mentors, Hometowns, and Weapons of Wit. All this makes powergamers get that twitch in their left eyes because it feels like making stats up on-the-fly during character creation.
Fluff and 40K
|This article or section involves Matt Ward, your Spiritual Liege, who is universally-reviled on /tg/. Because this article or section covers Ward's copious amounts of derp and rage, fans of the 40K series are advised that if you proceed onward, you will see fluff and crunch violation of a level rarely seen.|
With the exception of the cases of table-destroying crunch he's produced (Read: Grey Knights or Necrons post-sixth edition, WHFB Daemons, etc), the main reason people have for hating Matthew Ward (the monster stated above) is his horrendous mauling of the game universe's fluff.
Daemons crunch notwithstanding, rules-wise Matt Ward isn't that bad. Other than the Plasma Siphon, Force Weapon-equipped Dreadnoughts, Radiation Grenades, Terminators equipped with grenades, Deep-Striking Land Raiders...
...You know what? Fuck it. He's fucking terrible everywhere. But the ultimate source of most people's blinding hatred for the man is his slaughtering of fluff.
Baby carriers, the Monkey List, and the Khornate Knights are all among his top contenders for worst fluff abomination. Fluff matters more than anyone will admit, despite that when it is not respected, it's gonna be painful for everyone involved: see C.S. Goto. He didn't even touch the crunch, yet everybody hated him.
Examples of Fluff Overwhelming Mechanics
- In Games Workshop's official fluff for Warhammer 40,000, the Space Marines fluff describes them as extremely hardcore super warriors who regularly achieve kill-to-death ratios somewhere in the order of several thousand to one. When you actually play the game, the crunch of their statistics, are not nearly as good as the fluff would suggest, else a balanced game would require one Space Marine mini to be 300 points or greater. This is just when they fight alone, when they fight together they truly show their demi-gods of war status. Together, a squad of Iron Snakes in Dan Abnett's book "Brothers of the Snake" killed ten thousand Dark Eldar in one fight within a building whose ceiling was so high it could literally not be seen. By the end of the battle, the Eldar corpses were piled so high that the Space Marines had to stoop so as not to hit their head on said ceiling. This is also one of the few stories in which a Space Marine actively uses his acid spit in combat (to melt a Dark Eldar Archon's face).
- Tieflings in D&D4e have a history of a culture that long ago made pacts with devils, that have since expired and have no mechanical effect on the game. There are no rules that discourages good nor lawful good behaviour, and they gain no bonuses for being badguys, and yet players that use tiefling characters will always take the roles of sinister jerks. "But I played a tiefling that was all noble and selfless --" yeah, but you thought that made her a special unique snowflake, didn't you?