Scotch is a type of whiskey, and cognac is a type of brandy. As was said if you can't tell them(whiskey and brandy) apart there is something wrong with your taste buds. Whiskey is more like wine than most hard liquors, because it will age in the barrel and has a more complicated fermenting process, so there's more of a taste for it. I don't have it so much myself. Single malts mean its the same batch of grain in the same barrel usually aged longer, as opposed to cheap mixed whiskeys which is a big shitmix. For the hangover thing VC is right as well, something like Grey goose or Belvedere chilled with just a splash of something is nice and you don't feel it so much.