The world of this Dungeons and Dragons game is more or less Earthlike in fundamental ways. The ground is down below and the sky is up above, water flows downhill, things melt when they get hot, and so on. Beyond those fundamental ways, however, much is different.
This world is one where magic is one of the fundamental forces. Where our universe has magnetism and gravity, this one has forces of Socratian elements (fire, water, wind, and earth), pure good and evil and chaos and order, and the primal forces of nature. In our universe, the sun is a giant exploding ball of hydrogen ninety-three million miles away. In this world, the sun is literally the face of the sun-god Pelor as he journeys across the sky.
Virtually none of this is going to have a dramatic effect on gameplay, but it’s an important perspective to maintain: sometimes things work differently.
Dungeons and Dragons is a world of polytheism, where almost every sentient race has a patron pantheon, plus more for aspects of creation like the passage of time, or the sun and moon, or travel and commerce, or valor, or tyranny, or whatever. The gods themselves rarely intervene in day-to-day life, but are known to imbue mortals with a sliver of their powers in the forms of clerics and paladins. Not to be ignored is the primal power of nature itself; while not sapient in a way that any mortal can fathom (and thus not properly a “god”) it demands respect and can be tapped as a source of magic.
Another example: in our universe, human beings are the only sentient species. In this world, humans exist, but they’re new on the stage of history compared to the other races: dwarves and elves, goblins and gnomes, giants of various sorts, and of course, dragons. Humans have only been around some seven hundred years; since elves live to be around nine hundred years old, some can remember a time before anyone had ever seen a human being.
In regards to technology, the Age of Humanity has brought blindingly rapid advancement in the realms of technological progress (at least from the viewpoint of the older races). The first humans anyone met were savage and tribal, but these tribes of humans took the quasi-medieval concepts taught to them by the other races and have developed them into much more. The world is now at a level somewhat reminiscent of the Renaissance period in our universe, vaguely around the 12th or 13th centuries of history.
For instance, smelting iron and charcoal into steel is widely-known and utilized. Forming glass and grinding it into lenses is expensive but not unusual. Pulping plant fibers and bleaching them into paper is uncommon, and the moveable-type printing press hasn’t been invented yet — most books are still handwritten on vellum or linen parchment. The most common form of government is hereditary rule by a monarch with absolute power; humans are working on the forms of civil service and taxation they call “feudalism”. Most societies have a written code of laws as the cornerstone of their justice system, but the idea that a written document should (or even can) limit the powers vested in a monarch would seem patently absurd to almost everyone.
Gunpowder does not exist. The idea of determining where you are in the world by observing the steady movements of the stars has never occurred to anyone (mostly because Corellon Larethian, patron god of the elves, has a habit of repainting the night sky as a gift to his consort, the goddess of the moon Sehanine). The idea that the rights of the individual are more important than the rights of the state or the rights of the gods — modern liberalism — is a purely human idea, one that’s struggling somewhat to catch on. The old races are aghast at the very idea.
Each race treats the idea of gender equality differently. In the peasant castes of human societies and in most halfling settlements, men tend to work the fields and women tend to work in the home. Above the peasant caste, women and men are equally represented in the merchant, scribe, soldier, or noble parts of society. Elves and orcs simply don’t care about gender roles. Gnomes have rigidly-enforced roles for men and women. And given their propensity for keeping to themselves, their thick concealing clothing, and that women can and will proudly grow and wear beards, most races aren’t sure if any given dwarf they’re talking to is a man or a woman. (A common joke is that the first few months of dwarven courtship is spent politely figuring out whether the object of your affection is of a compatible sex in the first place…)
The base for this adventure is the small city on the border of the Frontier called St. Merridell. The character’s aren’t there yet, since there’s some stuff about Caravans and Adventure Starting Scenario to handle first.