I have recently become interested in Tolkien's work and have started reading The Silmarillion, so I am quite a beginner regarding the whole Tolkien universe.

The thing that confuses me is the eastern continent of Arda which bore the name "Middle-earth" long ago when Valar shaped the world. I can not seem to follow whether that name is still attributed to the entire continent (excluding the Dark Land which became separate landmass after Melkor destroyed the lamps) or only the northernmost region of it. This wiki page says that Middle-earth is north of Hither Lands which adds to confusion since those two regions belong to one piece of land.

I would appreciate if someone could clarify what exactly does the term "Middle-earth" encompass in The Lord of the Rings books.