Shochu

Shochu is a distilled alcohol made from a variety of plants, grains, and sugars that is centered around the town of Kagoshima, in southern Japan. The word Shochu comes from the Chinese for "burnt liquor" (in the way that brandy comes from the Dutch for "burnt wine"), and probably was brought to Japan in the mid-16th century from either India or Thailand by way of Okinawa. Most shochu is around 50 proof, but they can be as high as 70 or 80 proof. Most shochu is sold young, with maturation times post-distillation of around three months. 

There are two classifications of shochu: Singly-distilled (koshu) and Multiply-distilled (otsushu), and the requirements are different for each type:

Singly Distilled Shochu (AKA Group B)

• Typically made in a pot-still and bottled at no more than 90 proof
• Can be made from grains or plants (rice, barley, wheat, buckwheat), sake lees, or sweet potatoes (called imojochu), and koji.
• Usually drunk neat, on the rocks, or with water

Multiply Distilled Shochu (AKA Group A)

• Typically made in a column still and bottles at no more than 72 proof.
• Cannot be made from fruit or germinated grains
• Cannot be filtered through charcoal
• First made in the early 20th century and became legal in 1949
• Typically made from beet sugar or diluted molasses, like [ingredient=rum rum]
• Usually used in cocktails, or flavored with fruit and topped with club soda

Some other types of shochu are Awamori, made on the island of Okinawa from a long-grained Thai rice and black koji and what is called  "brown sugar shochu" from the Amami islands. 

There is a good chance that you're buying multiply-distilled shochu if it is inexpensive. Singly distilled shochu retains the flavor of the raw ingredients.