The yuzu's flavor is tart, closely resembling that of the grapefruit, with overtones of Mandarin orange. It is rarely eaten as a fruit, though in the Japanese cuisine its aromatic zest (outer rind) is used to garnish some dishes, and its juice is commonly used as a seasoning, somewhat like the way the lemon is used in other cuisines. It is an integral ingredient (along with sudachi, daidai, and other similar fruits) in the citrus-based sauce ponzu, and yuzu vinegar is also produced. Yuzu may be used to make marmalade or as an ingredient in cakes. It is also used to make liquor (such as yuzukomachi, 柚子小町) and wine.[1][2] Yuzu kosho (also yuzukosho, literally "yuzu and pepper"), is a spicy Japanese sauce made from green or yellow yuzu zest, green or red chile peppers, and salt. Slivered yuzu rind is also used to garnish a savory, salty egg-pudding dish calledchawanmushi, as well as miso soup.[3]
Yuzu is also known for its characteristically strong aroma, and the oil from its skin is marketed as a fragrance. In Japan, bathing with yuzu on Toji(the winter solstice) is a popular custom. The whole fruits are floated in the hot water of the bath (sometimes enclosed in a cloth bag), releasing their aroma.
Here is also a nice article from the New York Times On the Yuzu fruit
In Korean cuisine, yuzu (called yuja in Korean) is used, thinly sliced and combined with sugar and honey, to make a thick, marmalade-like syrup containing pieces of the chopped rind and fruit. A tablespoon of this syrup (which can either be made at home or purchased in glass jars) stirred into a cup of hot water makes a beverage called yujachaphoto (유자차; also spelled yujacha or yuja-cha, cha meaning "tea" in Korean), or, which is used as a herbal remedy for the common cold and similar winter illnesses.
It is also used to make yuja hwachae, a variety of traditional fruit punch.