Please pass me the book.

Used to refer to a specific person or thing that is known or can be identified.
The dog barked loudly.
She saw the car.
He ate the apple.
the end
the beginning
the middle
a
an
this
I saw the cat that was in the garden.

Used to refer to a person, thing, or idea that is already known or has been mentioned.
The dog barked loudly.
She read the book.
He likes the blue car.
the end
the beginning
the same
a
an
this