A cask is a type of barrel that is used to store and age alcoholic beverages, such as whiskey. Casks are typically made of oak, and the type of oak used can have a significant impact on the flavor of the whiskey. For example, American oak casks impart a sweeter, more vanilla-forward flavor, while European oak casks impart a more spicy, tannic flavor.
The size of the cask can also affect the flavor of the whiskey. Smaller casks allow for more interaction between the whiskey and the wood, resulting in a more intense flavor. Larger casks, on the other hand, allow for less interaction between the whiskey and the wood, resulting in a more mellow flavor.