In case you didn’t know, Cabernet Sauvignon is a wine (and grape) that originated in the Bordeaux region of France. Cabernet Sauvignon, the wine, is made exclusively from Cabernet Sauvignon, the grape, making it a pure varietal wine.
Red Bordeaux is a blended wine from the Bordeaux region of France. It consists of a blend of the juice from Cabernet Sauvignon, Cabernet Franc, Merlot, Petit Verdot, Malbec and Carménère grapes, all grown in the region.
So, in the simplest sense: Cabernet Sauvignon is a subset of Bordeaux wines that are made exclusively from Cabernet Sauvignon grapes. But this only applies to Cabernet Sauvignons produced in Bordeaux, otherwise it’s just another wine.