The nations and races of Warhammer are divided into factions. Factions are groups of nations and races that share a similar motivation. They often ally themselves either with those who are exactly like themselves, or with factions that are only slightly different. Factions tend to receive bonuses to their social skills when dealing with members of their own faction, or with those factions only slightly different from themselves.
Before character creation, it is imperative that the group of players determine what factions they want their characters to represent. This prevents the creation of an eccentric group that would never work in a setting that is so clearly defined (i.e., Dwarfs will never team up with Orcs, High Elves will never team up with Dark Elves, etc.)
Below are descriptions of each of the factions of Warhammer.
Order is the quintessential forces of good, light, and righteousness. They have determined that the forces of destruction, whether they be the servants of the Ruinous Powers, the Greenskins, the Skaven or the Dark Elves; seek to destroy all that is good and stable in this world. These foes have no place in the world and so must be vanquished. This faction dedicates itself to keeping the forces of darkness at bay, for the good of the entire world.
Fortune is the epitome of greed and avarice. This faction only concerns itself with the here and now. Life is hard enough, but with enough gold and power, one can have all he needs to make life comfortable, even extravagant. This faction tends to focus on constantly gaining new resources and not concerning itself with the balance of good and evil. After all, those who are determined to throw their lives away for such high-minded goals must eat too. Besides, those fools can be useful tools in increasing one's power. No army marches for free.
The world is in a constant state of flux, a shifting scale between Order and Destruction, Good and Evil, Light and Darkness, Life and Death. There are those who seek to keep the world in a never ending state of stasis (and some would say stagnation); a world in which Order and Destruction are evenly balanced, and never changing. For them, no force is "good" or "evil", and they determine their actions based on the shift of the scales.
The forces of darkness and the Ruinous Powers seek to destroy all that is. The Chaos Gods and their servants WILL assimilate and transform the entire world into an extension of the Realms of Chaos and the twisting warp within. Meanwhile the Greenskins simply seek to destroy and devour anything that they aren't. The Skaven have peered up from the numberless tunnels of their Under Empire and the time is at hand to bring the surface world crashing down into the darkness. All else is merely food.
The legacy of Nagash the Necromancer has haunted the world since time immemorial. Though five millenia have passed since his destruction at the hands of Sigmar, there are those within the Colleges of Magic and the temples of the Old World that know a time will come when the terrible lich returns with revenge on his ancient mind. Revenge against the descendants of the man-god. Even now his touch and influence are seen in the very existence of the Vampire Counts of Sylvania, and the Land of the Dead; his own homeland warped into a shadowy, gray, cold and silent world in which no heart beats. A world of oblivious slaves.