Single Malt Whisky
Scottish single malt whisky is a type of Scotch whisky, distilled by a single distillery in a pot still, using malted barley as the only grain ingredient. As with any Scotch whisky, a Single Malt Scotch must be distilled in Scotland and matured in oak casks in Scotland for at least three years (most single malts are matured for longer).
Malt; indicates that the whisky is distilled from a single malted grain. Not all grains can be malted (rye is another grain which can be malted), but in the case of single malt Scotch, barley is always the grain used.
Single indicates that all the malts in the bottle comes from a single distillery.
Multi-distillery malts are usually called blended malt, vatted malt
or (deliberately confusing, perhaps) pure malt.