Bourbon is a type of whiskey, just as Scotch is a type of whisk(e)y.
Here are the federal guidelines to be considered bourbon:
-must be at least 51% corn
-must be aged in new, charred oak barrels
-must be produced in the United States (anywhere, not just Kentucky)
-must be bottled at 80 proof or greater
-must come off of the still at no more than 160 proof
-must enter the barrel at 125 proof or less
The whiskey has to be aged for over two years to be called Straight Bourbon and anything less than four years must have the age stated on the bottle. Similar to Scotch, the age stated on the bottle must be the age of the youngest bourbon in the mix. There is no issue with the bourbon being older than what is stated, it just can't be younger.