Vodka is easily one of the world's most consumed distilled beverages. It is typically a colorless liquid containing ethanol purified by distillation from a fermented substance such as grain or molasses.
Vodka is generally drunk neat in its Eastern European and Scandinavian homeland, but growth in popularity elsewhere owes much to its use in cocktails and other mixed drinks, such as the Bloody Mary, the Screwdriver, the Vodka Tonic, and the Vodka Martini.
Except for various types of flavorings, vodka consists of water and alcohol (ethanol). It usually has an alcohol content ranging from 35% to 50% by volume. The classic Russian and Polish vodka is 40% (USA 80 proof). At strengths less than this, vodka drunk neat (not mixed with other liquids) can taste "watery" and above this strength the taste of vodka can have more "burn". Some governments set a minimum alcohol content for a spirit to be called "vodka". For example, the European Union sets a minimum of 37.5% alcohol by volume.
Background and History (courtesy of wikipedia.org):
The word is constructed as a diminutive of "water" in various Slavic languages (voda, woda, вода).
The percentage of alcohol can be attributed to the Russian standards for vodka production introduced in 1894 by Alexander III from research undertaken by the Russian chemist Dmitri Mendeleev. According to the Vodka Museum in Moscow, Mendeleev found the perfect percentage to be 38, but since spirits in his time were taxed on their strength, the percentage was rounded up to 40 to simplify the tax computation.