What is the importance of Numenor in the Unfinished Tales of Numenor and Middle-earth?

The island of Numenor is a land created for the people of Middle Earth by the Valar. The island is divided up into six specific sections that are defined by the lay of the land. Since the landmass is shaped like a star, each of the points is its own area with the middle portion making up the sixth section. Starting at the top of the island is Forostar, then moving to the west there is Orrostar, then Hyarrostarr, Hyarnstar, and finally Andustar. The center of the island is known as Mittalmar.