A double-distilled brandy from Cognac, France. Cognacs are graded by aging, 3, 5, or 7 years. According to Sharon Tyler Herbst "Label terms X.O., Extra and Reserve usually indicate a Cognac is the oldest a producer distributes."
You can purchase Cognac in most liquor stores or grocery stores with a well stocked liquor section. Additionally you can purchase this online at Bevmo.com.