The unifying characteristics of whisky are fermentation of grains, distillation, and ageing in wooden barrels.
Malt whisky is made from malted barley, grain whisky is made from any type of grain.
Whiskies only mature whilst in a wooden often oak or sherry barrel so the “age” of a whisky is only the time between distillation and bottling. This reflects how much the wood has interacted with the whisky, changing its chemical makeup and taste.
Most whiskies are sold at or near an alcoholic strength of 40% abv although the strength can vary.
Malts and grains are combined in various ways:
Single malt whisky is whisky from a single distillery made from a mash that uses only one malted grain.
Blended malt whisky is a mixture of single malt whiskies from different distilleries.
Blended whisky is made from a mixture of different types of whisky.
Whisky made in Scotland is known as Scotch whisky, or simply as “Scotch”.