The Mother World, more commonly known as just the world, was home to the Nelwyns, the dragons, the Daikinis, and many other races. It had a sun and a moon, and at night, many stars were visible in its sky, which aided navigators. Although most people considered the world to be flat and to have an end, dragons as well as sorcerers knew that the world was in fact a rotating ball floating in the middle of the universe.
There were twelve Great Realms (also called Great Domains) in the world, organized into three overlapping Circles encompassing four Great Realms each. The Great Realms of the Circle of the World were Earth, Water, Fire, and Air. The Great Realms of the Circle of the Flesh were Greater Faery, Lesser Faery, Daikini, and Malevoiy. The Great Realms of the Circle of the Spirit were Life, Death, Hope, and Despair. The area where these circles overlapped constituted a Thirteenth Realm.
The world featured two major landmasses: the Western Continent and the Eastern Continent. Much of the world was wild, heavily forested and inhabited only by frontiersmen and animals. The more settled parts of the world existed in a feudal culture, with sparsely settled kingdoms (ruled by kings and queens) subdivided into duchies and provinces (ruled by minor nobles). An exception to that rule was Nockmaar under the rule of Bavmorda: not only did she govern absolutely, without vassals, but the kingdom of Nockmaar lacked the population to fill more than one province in the southern kingdoms.
Behind the scenes
The fantasy world in which the 1988 film Willow takes place was never named in the movie itself. In the Chronicles of the Shadow War novels, it's simply referred to as "the world" and, in one instance, as "the Mother World."
In 2006, the world of Willow was named "Andowyne" in a series of databank entries published on April Fool's Day by StarWars.com. The update page indicated that the Chronicles of the Shadow War would be republished as a Star Wars omnibus, and that the Willow continuity would be added to the Star Wars continuity. Two days later, a disclaimer was added to the update page revealing that it had all been a joke. Therefore, the canonicity of the term "Andowyne" remains dubious at best.