In linking a subordinate clause and a main clause, a relative pronoun functions similarly to a subordinating conjunction. Unlike a conjunction, however, a relative pronoun does not simply mark the subordinate (relative) clause, but also plays the role of a noun within that clause.
The main ingredient in most vodkas is some kind of grain, such as wheat, corn or rye. Potatoes are another common base ingredient for vodka, according to About.com.
Vodka is traditionally made from potatoes but not always. Gin is flavored with juniper, but it is not a juniper berry wine. Both liquors are basically moonshine but with a controlled amount of alcohol. Gin in particular was often made on stoves and bathtubs from random ingredients during prohibition.