In the early days of British colonization of today's Virginia, the colonists attempted to sell tobacco to Europe. Blech! Europeans hated it. This was all
Nicotiana rustica.
Then a seed from the Orinoco River region of today's Venezuela was introduced. This was a larger leaf tobacco, that air-cured to a mellow character. It was the export of Orinoco tobacco (
Nicotiana tabacum) to Europe that turned Virginia into a successful narco-state.
Flue-curing did not exist back then. Since the late 19th century, Orinoco tobacco has been considered the prototypical flue-cure variety. But like the word "Virginia", the label of "Orinoco" is fairly non-specific. There are "Virginia" tobaccos that are air-cured, dark air-cured and dark fire-cured. Likewise with "Orinoco".
Billings
Compared to prototypical "Spanish" types, the leaves of Orinoco varieties tend to be longer rather than broader, the vein angle is more acute, and the leaf tip comes to a more pronounced point. But as with the entire world of tobacco varieties (which were unintentionally and intentionally allowed to hybridize for the past few thousand years), some "Orinoco" varieties are more agronomically developed than others. And they have been cured in multiple ways.
SUMMARY: It's a vague categorization.
Bob