J.R.R. Tolkien calls the world inhabited by Middle-earth’s peoples Arda.
In Tolkien’s mythology, Arda is the name for the whole world created within the larger universe of Eä. Middle-earth is only one major region of Arda, not the name of the entire planet. This distinction is one of the most common points of confusion in descriptions of Tolkien’s geography.
Arda changes across the ages. Its history includes the shaping of the world by the Valar, the destruction and transformation of lands, and the later dominion of the peoples of Middle-earth. The world’s central continent is separated from other regions by seas and changing coastlines.
Aman is the western land associated with the Valar, and Valinor is the region within Aman where many of them dwell. Beleriand is a land of the First Age that is later destroyed and submerged. None of those names refers to the complete world.