Gee, thanks for the patronizing answer.
What you found by Googling it is a whole bunch of stuff that me, a non-chemist, doesn't understand.
From what I remember from sophomore organic chemistry (about 30 years ago), the ethyl alcohol molecule has two carbon molecules. I'm guessing that the 'C12-15' refers to a longer chain of carbon atoms in this molecule.
If my assumption is right, why is there a range of 12-15? Wouldn't each of those constitute a different molecule with different properties?