What is the difference in single barrel and single malt whiskeys?

Jack Daniels is a brand of whiskey (one of the most famous). It is classed as a Tennessee Straight whiskey (made primarily of corn) which is like Bourbon whiskey except the raw distillate is filtered through charcoal prior to barrel aging.

"Single malt" is a class of whiskey that describes it as being entirely the end product of a single malted grain (barley or rye are prime candidates) at a single distillery. Well-aged Single Malt Scotch whiskey is considered among the most prestigious whiskeys in the world.