What exactly is achiote other than ground annatto seed? I picked up a packet
at my Mexican meat market and while it seems to smell somewhat like American
barbecue sauce, when I used it it did not seem to taste the same.

I'm only familiar with annatto as a coloring ingredient in American food, I
can't recall seeing it being used for flavoring. I mixed my achiote with a
bit of vinegar and it stunk to high heaven, but the package also suggested
I mix it with olive oil. I live on the Mexican border and in my experience
I cannot remember eating Mexican food with achiote in it, so it might be
something more common in the interior.