Cognac is a type of brandy that is strictly controlled, having the designation Appellation d'Origine Controlee (AOC) which can be translated as "controlled designation of origin". As such it is only allowed to be produced from grapes grown in the region surrounding the town of Cognac, France.
Calvados is an apple brandy from the French region of Basse-Normandie or Lower Normandy.
Armagnac is a distinctive kind of brandy produced in the Armagnac region in Gascony, southwest France. It is distilled from wine usually made from a blend of grapes including Ugni Blanc, Colombard, and Baco 22A, using column stills rather than the pot stills used in the production of Cognac.