Whenever you hear the words Brandy, Cognac or Whisky, a huge guy with a big Cuban cigar comes to mind. This is because they are associated with wealth and class. Often time people find it difficult to even differentiate or distinguish between the drinks, as they have similar tastes.

Below are the differences in this spirit drinks;

Brandy
Brandy is short for "Brandywine" and it is produced by distilling wine and aging it in wooden casks to mature for drinking. Sometimes caramel coloring is added to the drink to imitate the effects of aging, while some brandy drinks are produced with the combination of both aging and coloring. Brandy contains about 30 to 60 % alcohol per volume and it’s usually taken after dinner as digestifs.

Varieties of Brandy
Armenian brandy
Armagnac
Cognac
Cyprus brandy
Dried fruit brandy
Greek brandy
Brandy de jerez
Konyak
Pisco
South African brandies
Italian Stravecchio
Grades of Brandy
V.S. ("very special"
V.S.O.P. ("very superior old pale"
XO ("extra old" or napoléon
Hors d'âge ("beyond age"
The grades can be found near the drinks brand names on the bottle.

Cognac
Cognac or konyak is a variety of Brandy made from grape, named after a town called cognac in France. To produce cognac, two distillations are done in traditional charentais, copper alembic stills, after the grapes has been pressed and the extracted juice fermented for about three weeks, leaving the wild yeasts to covert the sugar into alcohol with up to 70% per volume. Cognac is aged in limousine oak casts for about two years before they are bottled and sold publicly. The longer cognac stays in the limousine oak casts, the lesser its alcohol volume this is due to a phenomenon called la part des anges (reduction in alcohol level).

Grades of Cognac
V.S. (Very Special)
V.S.O.P. (Very Superior Old Pale)
XO (Extra Old) or Napoléon to Hors d'âge (Beyond Age).
Whisky
Whisky is a distilled alcohol beverage produced from fermented grain mash. Whisky is aged in American or French oak casks. During the aging period the whisky undergoes extraction, evaporation, oxidation, concentration, filtration and coloration to achieve the final flavor. To distill special flavors of Whisky, malts and grains are combined in various ways such as single malt whisky, blended malt whisky, blended whisky, cask strength, single cask to produce unique flavors. Whisky drinks contains about 40% alcohol by volume.

Varieties of Whisky
American whisky
Australian whisky
Canadian whisky
Danish whisky
English whisky
Finnish whisky
German whisky
Indian whisky
Irish whisky
Japanese whisky
Scotch whisky
Swedish whisky
Taiwanese whisky
Welsh whisky

more at https://www.supermart.ng/blog/know-your-brandy-cognac-and-whisky.html