"It is a man."
Translation:Det er en mann.
Yes, Norwegian is even simpler than English in this regard. No declension of verbs in the present tense.
This is a good man and we don't want him to feel like a thing or an animal. In this example, we use it to state that that particular person is a man by using the obligatory neuter singular form - det. Before a noun is introduced, the demonstrative pronoun used is always det.
Det er en bok. Den er interessant. (It is a book. It's interesting.)
Det er et insekt. Det er farlig. (It is an insect. It's dangerous.)
When you want to refer to that noun, you have to change the demonstrative pronoun according to its gender (den - masculine/feminine, det - neuter).
However, this is used only to refer to animals and things, not human beings.
Den and mann can "go together" in the following example.
Hvilken mann? Den mann. - Which man? That man.
Just using den would be incorrect in this case as well because you're not referring, you're pointing to the criminal that stole your ice cream.