Whisk(e)y is spelled with the e (whiskey) if it is from Ireland or the US and is spelled without the e (whisky) if it is made elsewhere.   Whiskey, or whisky, is alcohol distilled to a minimum of 40% and maximum of 94.8% alchohol by volume (ABV) and largely from fermented grain mash, which is a base mixture of grain and water.  Whiskey is typically aged in casks made of charred white oak with different grains like barley, corn, rye, and wheat being used for different whiskey varieties.  The type of whiskey can be distinguished by its country of origin and the type of grain used in the distillation process.  The types of whiskey include, but are not limited to, rye whiskey, bourbon whiskey, scotch whisky, Irish whiskey, and Canadian whisky.  Types of whiskey can also be categorized as being malt, grain, corn, or blended.

Scotch

Scotch whisky is whisky made entirely in Scotland and must be made from water and malted barley, but whole grains of other cereals may also be added.  The malted barley is often dried over peat smoke, which gives scotch its smoky flavor.  Scotch must also be aged in oak casks for at least three years and one day in Scotland and is generally distilled twice in pot stills, but a few are distilled three times.  

Irish

Irish whiskey is typically distilled three times and must be produced in Ireland and be aged for at least three years in wooden casks.  Similar to scotch, Irish whiskey must include malted barley and may include other unmalted cereal grains.  Furthermore, Irish whiskey is often made from kiln-dried barley, which gives it a smoother taste than the smoky overtones that are common in some scotches.  

Canadian

Canadian whisky is often referred to as rye whisky, even though there are no requirements for rye to be used in the distillation process.  Canadians use a variety of mash bills, a combination of grains in different proportions, and most of their whiskies are blended after maturation with multi-grain liquors that contain a large percentage of corn spirits.  historicaly, highly flavored rye grain was added to the mash and people began calling this new style of rye-flavored whisky as rye in order to distinguish it from other whiskeys like bourbon.  Today, Canadian law requires that whisky labeled as Canadian Whisky, Canadian Rye Whisky, or Rye Whisky be aged for at least three years in Canada and any spirit used in the making of Canadian whisky must be aged in wooden barrels, used or new, with a capacity of 700L or less.

Bourbon & American

Bourbon is an American whiskey distilled from a mash that is at least 51% corn and its name comes from the geographic area known as Old Bourbon in Kentucky.  As an American whiskey, it must be aged in new charred oak barrels and must be distilled to a maximum of 80% ABV (160 proof).  Other American whiskeys include rye, rye malt, malt, wheat, corn, and Tennessee whiskey, which has almost identical requirements to bourbon, but must be made in Tennessee and be charcoal-filtered before it is filled into casks.  Straight bourbon must be aged in the new oak barrels for at least two years and be made from a single batch.  It must be unblended and, essentially, be straight from the barrel.

Rye

Rye whiskey can refer to either American rye whiskey or Canadian whisky.   American rye whiskey contains at least 51% rye and must be aged in oak casks for at least two years.  Since American law calls for several requirements in order to label a product as rye whiskey, the vast majority of Canadian rye whiskies cannot be sold in the United States as rye whisky.

Corn

Corn whiskey is an American liquor produced from mash that is no less than 80% corn.   Unlike other American whiskeys, corn whiskey does not need to be aged.   If it is aged, it's typically for 6 months or less and it must be in used or uncharred oak barrels.

Malt

Malt whisky is made predominantly in Scotland and from mash primarily consisting of a malted grain, presumably barley.  It is distilled twice in pot stills and can be called single malt whisky if produced exclusively at a single distillery that only used a single malted grain.  Furthermore, in Scotland or Ireland, for a whisky to be considered malt whisky, it must be made from mash consisting of 100% malted barley.

Grain

Grain whiskey is made mainly from corn and barley, but can also contain wheat or rye and not include barley.  Similar to single malt whisky, single-grain whiskies are made from a single distillery, but with the addition of other cereal grains, typically wheat, corn or a blend, instead of just malted barley.

Blended

Blended whisky, or blended whiskey, is made by combining different types of whiskies from different distilleries.  Typically, blended whisky contains a blend of barrel aged malt whisky and grain whiskies.   However, there are also blended malt whisky and blended grain whisky, which is the combination of single malt whiskies and single grain whiskies, respectively, from different distilleries.