Jack Daniel's Single Barrel Rye Whiskey is the part of the brand's Single Barrel collection, a range of whiskeys selected from individual barrels located in the "uppermost reaches of [their] barrelhouses, where dramatic temperature changes cause the color and taste to reach their most intense." It's a premium product, as well as Jack Daniel's first release of a rye whiskey (their first new mash bill since the end of Prohibition, apparently). It's bottled at 94 proof.
Jack Daniel's is the producer of the single best-selling American whiskey in the world. Ironically enough, their home county of Moore is a dry county, prohibiting any alcohol sales within its borders.