Middle-earth is the setting of much of J. R. R. Tolkien's legendarium. The term is equivalent to the term Midgard of Norse mythology, describing the human-inhabited world, i.e. the central continent of world of Tolkien's imagined mythological past. Tolkien's most widely read works, The Hobbit and The Lord of the Rings take place entirely in Middle-earth, and Middle-earth has also become a short-hand to refer to the legendarium or its "fictional-universe".
Within his stories, Tolkien translated the name "Middle-earth" as Endor (or sometimes Endórë) and Ennor in the Elvish languages Quenya and Sindarin respectively, sometimes referring only to the continent that the stories take place on, with another southern continent called the Dark Land.
Middle-earth is the central continent of Earth (Arda) in an imaginary period of the Earth's past (Tolkien placed the end of the Third Age at about 6,000 years before his own time), in the sense of a "secondary or sub-creational reality". Its general position is reminiscent of Europe, with the environs of the Shire intended to be reminiscent of England (more specifically, the West Midlands, with Hobbiton set at the same latitude as Oxford).
There was a man who was cursed by the gods
To walk this land forevermore
Never to rest never to find peace
Trapped in this world for an endless journey
Offering his sword to the highest bidder
Fighting for whoever pays the most
No fear in his eyes, he knows he can't die
Taking a life is as easy as breathing
Yet another war to fight
He doesn't feel a thing
He has seen this a thousand times before
His mind is numb
What could a man have done
To so awaken the wrath of the gods?
Never to rest never to find peace
Trapped in this world for an endless journey
Can there be a fate more horrid
Than the curse of immortal life?
Still he wanders the grounds of this dark realm
Never finding a place to call home
Yet another war to fight
He doesn't feel a thing
He has seen this a thousand times before.
His mind is numb
He stands under a crimson sky
Alone as centuries pass by
Offering his sword to the highest bidder
Fighting for whoever pays the most
No fear in his eyes, he knows he can't die
Taking a life is as easy as breathing
There was a time when he picked the wrong side
There was a time when the war was lost
The entire army was crushed down to nothing
Only one man rose from the ashes
He didn't feel a thing
His mind is numb
Imagine a life where no one can stay by your side
What it's like to watch countless of your own children die
He is nothing but an empty shell
Will he ever get to embrace death?
In the shadows he's dwelled for thousands of years
Seen nothing but death
Only when the sun sets for the last time