What kind of car is it? Hva er det for en bil? / Hva er det for slags bil? What kind of sound was that? Hva var det for en lyd? Hva slags lyd var det? What is it? Hva er det for noe?

That last one literally translates to just "Hva er det" but it is very common to add "for noe" in Norwegian. What's that something? "Ikke noe" Nothing. But Duolingo often prefers literal translations as long as it doesn't disturb the meaning. Hva er det for noe? (Or "Er det noe?"), can also be asked to a person when you wonder if there's something wrong (are you upset or hurt etc, what's the matter). It's a Norwegian phrase where you are free to answer either "Ikke noe" or actually pour your heart out. (Hvordan går det? (How is it going) is even less committing, just answer Bra)

Den does not mean the masculine article here, it is the "pointing finger" equivalence (that brand), you would emphasize den when speaking.