The fictional continent where Tolkien’s Middle-earth stories mainly take place is called Middle-earth. It is the central region of Tolkien’s imagined world and the primary setting of The Hobbit and The Lord of the Rings.
Middle-earth contains locations such as the Shire, Rivendell, Moria, Rohan, Gondor, Mordor, and the Misty Mountains. Its peoples include Hobbits, Elves, Dwarves, Men, Orcs, and Ents.
The name does not mean a planet located between other planets. Tolkien adapted the term from the older Germanic concept of a central inhabited world, related to Old English middangeard and the Norse miðgarðr. He used it as part of a mythic history of Earth rather than as the name of an entirely separate planet.
Middle-earth is also only part of Arda. Aman lies to the west, and Númenor was an island kingdom later destroyed in the Second Age.