Sturgeon caviar is the traditional caviar that is quite often called "black caviar". Basically, it comes from the Sturgeon (Acipenser Baerii) also known by its Russian name Osetra or from other members of this vast fish family like Sevruga, Sterlet, American White Sturgeon, Kaluga, Hackleback etc.
Of course, all sorts of Sturgeon caviar are different in taste but they do have similar common features — the buttery flavor and very soft and tender structure. The Sturgeon caviar is usually prepared Malossol which means "little salt" that allows to preserve and emphasize the natural flavor.
Nowadays all the black caviar is produced from farm raised fish raised in commercial fisheries in different countries. But don't be afraid, it doesn't influence the taste — the fish is kept in the ponds with drink quality streaming water under temperature close to their original environment and fed with balanced natural nutrition.