Short answers, pulled from the story.
Middle-earth derives from the Old English word middangeard, whose second element originally meant "enclosure", cognate with the English word "yard". The same root produced the Old Norse Midgard of Norse mythology. Tolkien described it as meaning "the abiding place of men" - the physical world where human life is lived, situated between the unseen realms of heaven above and hell below.
Tolkien first encountered the term middangeard in 1913 or 1914, while studying an Old English fragment from the Crist I poem by Cynewulf. The fragment read: "Eala earendel engla beorhtast / ofer middangeard monnum sended" - "Hail Earendel, brightest of angels / above the middle-earth sent unto men." The name Earendel in that fragment inspired his character Earendil.
Tolkien placed Hobbiton and Rivendell at roughly the latitude of Oxford, England. Minas Tirith, six hundred miles to the south, corresponded to the latitude of Florence, Italy, while a separate annotation placed it at the latitude of Ravenna. The Mouths of Anduin and the ancient city of Pelargir fell at approximately the latitude of ancient Troy. Tolkien also used Belgrade, Cyprus, and Jerusalem as reference points.
The Rings of Power were magical rings whose fate dominated the Second and Third Ages of Middle-earth. Sauron forged the One Ring to give him the power to control or influence those who wore the other Rings. The struggle over the One Ring forms the central conflict of The Lord of the Rings.
The Lord of the Rings: The Return of the King received eleven Academy Award nominations in 2003 and won all eleven, matching the totals previously awarded to both Ben-Hur and Titanic.
The Istari were five Maiar - lesser angelic spirits - embodied and sent to Middle-earth by the Valar to help the free peoples resist Sauron. The most important were Gandalf the Grey, who remained faithful to his mission, and Saruman the White, who became corrupted and sought to rival Sauron for power rather than defeat him. A third named Wizard was Radagast.