What is "oerth"

In the Dungeons & Dragons roleplaying game, Oerth is the name of the fictional planet on which one of the earliest campaign settings, the World of Greyhawk, is located. Oerth has an axial tilt of 30 degrees, which would cause greater seasonal temperature variation than on Earth, were it not for wizardly and divine magic that shifts weather patterns to be more favorable to the populace (at least the god-fearing folks).