Armagnac is a type of brandy from the region of Gascony in southwestern France, centered around the town of Condom (yes, really. Condom). It was granted Appelation d'Origine Controlee (AOC) status by the French government in 1936. Armagnac is divided into three regions: Bas Armagnac, Armagnac Ténarèze, and Haut Armagnac. Recently, a new category of unaged Armagnac called Blanche d'Armagnac was created.
Armagnac was already widely recognized in the 14th century, making it the oldest distilled brandy made in France. It predates Cognac by two centuries.
Armagnac is similar to Cognac in a few ways, namely, that they use the same grapes to make the base wine (Ugni Blanc, Colombard, and Folle Blanche). Armagnac differs in important ways, though: Only one distillation instead of two with Cognac, in a column still instead of a pot still, and the oak used is the local black oak that is much more powerful and rustic in flavor profile.
The single distillation and the particular oak used to make Armagnac means that while there is plenty of flavor in Armagnac, it needs a long time in barrel to be drinkable. There are plenty of small producers of Armagnac, and many of them make vintage dated products.
Labelling requirements for Armagnac are similar to Cognac. VS (Very Special) on the label guarantees two years in a barrel. VSOP (Very Special Old and Pale) means at least five years of aging, and XO (eXtra Old) requires six. Above that, there is a category called Hors d'Age, where the spirit rests in barrel for ten years or more. It is more important to buy older Armagnac than Cognac, all other things being equal.
Some quality producers of Armagnac include Cerbois, Marie Duffau, Darroze, and Tariquet.