From the introduction:
Welcome to the world of Golarion! Scattered across the land lie an innumerable number of cultures and empires. Ancient Kingdoms have risen and fallen, leaving great wealth and powerful weapons to those able to claim them. The world is wide, but much of the events of note occur in a region known as the Inner Sea, with the City at the Center of the World, Absalom, housing many great and renowned institutions, notably the Pathfinder Society. But besides the Inner Sea, there are practically endless opportunities, notably in places like Tian Xia, where a certain Varisian tavern-owner may soon find herself heir to the throne, and beyond Golarion itself, there are the planes (Independent realities separate from Golarion) and other worlds sitting beyond the great gulf between the worlds, including Earth!