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).
It's not in the song I sing
Not in the gift I bring
Not in the words I say
Or the promise I've made to You
It's not in my hands held high
Not when I close my eyes
Not when I'm on my knees
For the world to see my faith in You
It's a way of life
It's a sacrifice
It's faith made sight
It's living right
It's a way of life
It's not in the truth I know
It's not in the works I show
It's when my eyes can see
What my heart believes
That we love You
It's a way of life
It's a sacrifice
It's faith made sight
It's living right
It's a way of life
It's a sacrifice
It's faith made sight
It's living right
It's a way of life
Here is my life
May it be holy and pleasing Lord to Thee
All that I am
I will bring as my offering
It's in the life I live
It's in the love I give
It's the things I do in Spirit and Truth