Why is whiskey aged in wood barrels?

Aging in wood barrel imparts desirable flavors in the unaged whiskey over time and makes it smoother to drink. Most commonly used wood for producing barrels is oak. Unique characteristics found in oak impart commonly recognized flavors like vanilla, coconut, cocoa and tobacco to the aged whiskey. Many producers also char the insides of the barrel before using them for aging whiskey, providing additional layer of flavors to the aged whiskey. Barrels used to store rum, sherry, port and other fortified wines are also used to create unique combination of flavors.