Scotch is made from malted (read sprouted) barley which is then dried, usually by heating with peat hence the varying degrees of smokiness, which is fermented, distilled then aged. Must be produced in Scotland.
Single Malt: Whisky ( note lack of “e” ) or to whiskies ( again note Scottish spelling) It means that the whisky comes from a single distillery and is not blended with whisky from another distillery- which if it was would make it either a batted or blended whisky,  but is probably the blending of a multiple barrel “dump” as it is called in the industry to create a distillery signature and consistent style.The barrels chosen usually represent a distillery style or signature that while consistent will vary within a certain range to keep peoples interest but be identifiable as that companies product. Barrels too far outside the style are not selected and many times will be sold for blending or as a merchant bottlings
Single Single or Singleton: A single malt but from one single barrel – not mixed with other barrels.These are rarely done by the distilleries themselves and are usually encountered as merchant or independent bottling. You have to read the labels carefully as a merchant or independent bottling can be either a single malt or single single. If it is a single single it is usually referred to as a single cask bottling or singleton.