Types of Alcohols and Spirits

Early settlers in United States made whiskey from Rye. The whiskey had to be aged to take the harsh bite out

During prohibition, all the distilleries were shut down. After the prohibition was lifted, there was no 'aged' whiskey and the consumers turned to Vodka and Gin. All spirits are 'aged' except for Gin and Vodka. At present, Vodka is number one spirit sold in United States.

American Whiskey

American whiskeys are distilled from fermented mash of Rye, Corn, Wheat and malted Barley to 95% alcohol level still retaining the flavor of original mash. The whiskeys are aged in Oak barrels (except Corn Whiskey), and bottled at 40%alcohol. An aged whiskey for more than 2 years is designated as "Straight".
Rye whiskey must contain at least 51% Rye in the grain mash.
Bourbon whiskey must contain at least  51% corn in the grain mash.

Legally, Bourbon can not be produced by any other country than Unites States.

Corn Whiskey must contain at least 80% Corn in the grain mash. 

Canadian Whisky

In Canada there are no standards that dictate the type of grains, or percentages thereof in the mash. Primary grain is Rye, always blended with other grains resulting in smoother taste.

Scotch Whisky

Primary grain in Scotch whiskey is malt barley that is dried over peat fire giving it the Smokey flavor. Other grains are blended like corn and rye. "Single Malt" scotch comes from s single distillery. "Blended Scotch" is a blend of scotches from different distilleries as well as Neutral Grain Spirits (NGS) to achieve the brand's unique flavor. "Pure Malt" is a blended Scotch without any non-Scotch spirits. Scotch whiskey can only be made in Scotland.

Irish Whiskey

Irish whiskeys are made exactly like Scotch and adhere to same definition of categorization. The only difference between Scotch and Irish whiskey is that malt barley is not dried over peat fire. Irish whiskey can only be made in Ireland.

Vodka

Vodka can be made from any types of grains and even potatoes. Distillation process consists of multiple distillation and charcoal filtering till it is reduced to Neutral Grain Spirit ("without distinctive character, aroma, taste, or color." according to US law). The NGS is diluted by water to get the needed alcohol level. Vodka is not aged. Vodka is normally associated with Russia and Poland.

Gin

Gin can be made from any types of grains just like Vodka. After original distillation, it is re-distilled with Juniper berries and other herbs such as Cardamom, Cassia, Fennel etc. The primary flavor is derived from Juniper berries. During British Raj, the herbs reminded British of herbs used in Indian Cooking. So Bombay Gin was born as a marketing ploy. Gin in not aged.
Gin is an British slang name from Genever, the Dutch word for juniper.

Rum

Rum is made by distilling fermented sugar canes to 95% alcohol. In United States, most of the Rum comes from Caribbean Islands. Rum is bottled at 80 proof.
India produces the best rum in the world. India lacks the marketing and production capability to compete world wide. In India Rum is bottled at 85.6 proof.

Tequila

Tequila is made from fermented Agave Tequilana Weber (``blue'' variety) mash and legally must be produced in  Jalisco (Mexico). Tequila produced outside of Jalisco is known as "Mezcal". Tequila and Mezcal are bottled at 80 proof.