"Carbon" is used here as a description. It means something that is absolutely 100% exact of another. Not similar, not related, not sort of like,
neat a
cheap copy but absolutely the same. Down to the carbon molecules. A carbon copy if you will.
"Henna, do you remember that
key you gave me the other day to access the locked cabinet in Mr. Senner's office ?"
"Yeah, I do."
"Opening it I found a copy of the
key sitting on the bottom. Carbon."
"That's
strange. There's only supposed to be one. What good does it do in there ?"