VS and VSOP are terms that act as a guarantee of how long a Cognac has been aged.
They were introduced in 1983 following a request by the BNIC (Bureau National Interprofessionnel du Cognac) and the French government, who drafted regulations governing the terms used to describe a cognac’s quality. Just as with age statements in Scotch, these designations refer to the age of the youngest eau-de-vie used in making the cognac.
VS stands for Very Special and only eaux-de-vie at least two years old can be used to make a VS Cognac. Other denominators and expressions are permitted in this class, such as "3 stars" or "luxury".
VSOP stands for Very Superior Old Pale. VSOP cognacs are created from eaux-de-vie aged for at least four years. The VSOP class includes designations such as "Old" or "Reserve".
XO stands for Extra Old and XO Cognacs are made only from eaux-de-vie at least ten years old. Historically the minimum age was six years old, but it was increased to 10 years in April 2018.
Cognacs such as "Napoleon" or "Old Reserve" are terms that are deemed equivalent to XO Cognac.