Caviar is a name given to the unhatched roe of fish in the sturgeon family. It is also used as a generic term for the edible roe of any fish.
True caviar comes from either the Beluga, Sevruga, or Ossetra sturgeons. Due to its rarity and popularity it is very expensive.
In recent years there has been an embargo on some caviars in the United States due to the overfishing and rarity of the fish.