The Greyhawk setting was the first campaign setting created for the Advanced Dungeons & Dragons game. This setting is a place where almost anything is possible, a fantasy land where humanity shares a world with elves, dwarves, dragons, giants, and other creatures of myth, folklore, legend, and elsewhere. Magic is superior to technology here; wizards cast great spells, and warriors wield enchanted weapons against monstrous foes.
The land of the Greyhawk setting is called the Flanaess (fla-NESS), an eastern peninsula on a vast continent called Oerik (OH-rik), on a world known as Oerth. Oerth is much like Earth in nature and climate, though with many differences as well. Oerth has two moons, for instance, Luna (a great white moon) and Celene (a smaller aquamarine moon). The calendar followed by inhabitants of the Flanaess has 364 days, divided into 12 months of 28 days each, with week-long holidays between each season. Summertime is long in the Flanaess, winter is mild, and crops are usually good. Magic may be responsible for this.
The Flanaess is a European-like region where a central group of numerous kingdoms and states, great and petty, struggle for supremacy and survival against countless foes. A widespread conflict called the Greyhawk Wars greatly damaged the fabric of life here a handful of years ago. Armies of humanoids -- brutish creatures with human and bestial features -- march across the land. Giants and extraplanar monsters lay waste to civilization. A decaying empire breeds lawlessness and debauchery in its realms and threatens its neighbors. A mysterious elite order holds several nations in its evil grip. A vile demigod rules a northern empire as a tyrant. Barbarians, assassins, and monsters run rampant.
Yet the Flanaess is alive and vibrant, and it has great hope for its future. Adventurers strike out against the enemies of civilization and order, uncover lost and forgotten treasures, and gain the magic and monies they need to become the new heroes and leaders of their time. There are captured lands to be retaken, artifacts to be rediscovered and used, and incredible lands beyond the Flanaess to explore. It is an age of adventure with no limit to what one person can achieve.