Cognac and whiskey are both types of distilled spirits, but they are made from different ingredients and using different processes. Here are some of the key differences between the two:

1. Ingredients: Cognac is made from white wine grapes grown in the Cognac region of France, while whiskey is typically made from malted grains, such as barley, rye, or corn.
2. Distillation: Cognac is double-distilled in copper pot stills, while whiskey is usually distilled in column stills.
3. Aging: Cognac is aged in oak barrels for a minimum of two years, while whiskey can be aged in a variety of barrels, including oak, for varying lengths of time.
4. Flavor: Cognac has a light, floral, and fruity flavor with hints of vanilla and caramel, while whiskey has a more robust, smoky flavor with notes of wood, grain, and spices.
5. Serving: Cognac is traditionally served in a snifter or tulip-shaped glass to enhance the aroma, while whiskey is often served in a tumbler or rocks glass.

In summary, cognac and whiskey are both complex and flavorful spirits with distinct differences in their ingredients, production methods, and flavor profiles.