What is Whisky?
On a basic level, all whisky is distilled alcohol made from some kind of fermented grain, usually barley, rye, wheat or corn and aged in wooden casks. The type depends on where it was made -- there are a large number of different regulations around the world that define what can be called whisky.
Scotch is whisky made in Scotland, and it must be aged in oak for a minimum of three years. Seems simple, right? It is, though there are wide number of varieties. It typically has a smoky or peaty taste, though the tastes vary widely from distillery to distillery. Here are the 5 basic types: Single Malt
Whisky made from only water and malted barley at a single distillery. Single Grain
Whisky made from water and malted barley and other grains at a single distillery. Blended Malt
A whisky made from a blend of single malts from two or more different distilleries. Blended Grain
A whisky made from a blend of single grains from two or more different distilleries. Blended Scotch
A whisky made from a blend of single malts and single grains.
Irish whiskey is typically smoother and less peaty than scotch, but must also be aged at least three years in wooden casks. Any Irish whiskey made from more than one distillate is called a "blended" Irish whiskey, which is most of the big name brands, like Jameson, Powers and Bushmills Original.
Bourbon is a kind of whiskey that must be made in the U.S., and it almost all comes from Kentucky. It must be made from at least 51% corn and aged in new charred oak barrels for any length of time, though most are aged for at least four years. It's typically a little sweeter. Single barrel simply means that all the bourbon in the bottle comes from the same barrel, rather than being a blend of different barrels.
Other Types Of American Whiskeys
Rye whiskey (made of at least 51% rye) is another popular American whiskey. All American whiskies (including bourbon) must be aged in new oak containers, except for corn whiskey (minumum 80% corn), which needn't be aged at all.
Almost all Japanese whisky is made in the style of a single malt Scotch, though they are far less peaty than Scotches.