What is Denver's head?
He's a head, duh!
Is Denver's head a human head?
Yes in fact Denver's head used to be part of a living human body.
Then why does he look like that & why is he so small?
He looks like that because of a number of reasons: years of decay, neglect and lying in the sun too long.
If he is no longer living tissue, then how can he have feelings?
The soul of Denver's head is trapped inside him (just the soul of the head, not the rest of the body). He has emotions but cannot express them, because he is a decaying head. He know's what he is and that he once belonged to the body of a guy named Denver, unfortunately he does not remember any of Denver's history, or indeed how he came to be detached from him.
If Denver's head can not communicate or express emotion, then how can you know what he's thinking?
I have special pyshic powers and abilities which mean that i can hear what the dead are thinking. I am the only one able to communicate with denver's head, which is why i decided to take it upon myself to narrate his life.