Birch is a hardwood tree closely related to beech and oak. The tree is known for its generally light-colored bark in shades of gray, yellow, white, silver or occasionally black, which peels in the form of thin paper-like sheaths. Wood of the birch tree has an attractive sheen, and extracts of birch tree were once used in the production of wintergreen (methyl salicylate). Birch extract today is more commonly used as a flavoring agent, for scenting leather, and in the production of birch-tar oil, which lends both wintergreen and leathery notes to perfume, as well as in the production of birch beer, a fizzy soft drink similar to root beer in aroma and flavor.