What are the key differences between cognac, brandy, whisky, and bourbon?

Cognac and brandy are both types of distilled spirits made from grapes, with cognac specifically coming from the Cognac region in France. Whisky is a distilled spirit made from grains like barley, corn, rye, or wheat, and Bourbon is a type of whisky that must be made in the United States and contain at least 51 corn in its MASH bill. Each of these spirits has unique production methods and flavor profiles.