Bourbon is an American whiskey; a barrel-aged distilled spirit made primarily from corn. All bourbon is whiskey but not all whiskey is bourbon. Bourbon's legal definition varies somewhat, but many trade agreements require that the name "Bourbon" be reserved for products made in the USA.

In 1964 the U.S. Congress declared bourbon to be a "distinctive product of the United States". According to Federal Standards, bourbon made for U.S. consumption must be:

1) Produced in the U.S.

2) Made from a grain mixture that is at least 51% corn. (Most distillers use 65 - 75%.)

3) Stored and aged in new barrels made of charred oak. (Generally American white oak.)

4) “Straight” bourbon has additional legal requirements beyond those of regular bourbon; it must be at least two years old. If it's older than two but younger than four years, it must carry an “age statement” which reflects the youngest bourbon in the bottle. Finally, straight bourbon may not contain added colorings or flavorings.

After aging, barrels may remain saturated with as much as 10 gallons (38 liters) of bourbon, though 2–3 gallons (8–11 liters) is average. By law barrels cannot be used again for bourbon; used ones are often sold to distilleries in other countries, for aging other spirits.

Although bourbon may be made anywhere in the U.S. it is closely associated with the southern states and with Kentucky in particular. A staggering 95% percent of all “true” bourbon in the world comes from Kentucky.

More Info: en.m.wikipedia.org