There is no difference in formula between Brandy and Cognac.
Brandy is an abbreviation of brandy-wine and is any spirit distilled from either wine or fermented fruit juice.
Cognac is also a brandy but is so called because it is exclusive to the Cognac region of France.
The word brandywine comes from the Dutch brandewijn, which means “burnt wine,” because the drink is distilled.
All brandywine or brandy is “burnt” or “distilled wine.”
Some types of brandies are:
ouzo, flavoured with anise and originating in Greece;
grappa, distilled from the crushed residue from wine-making and originating in Italy;
kirsch, distilled from cherries and originating in Germany;
slivovitz, produced from crushed plums and originating in the Balkans;
and calvados, created from fermented apple cider and originating in France.