Caviar has come to be defined generally as fish roe, but technically, true caviar comes only from the sturgeon. The source of the best caviar is the Black Sea and the Caspian Sea. There are three types of sturgeon caviar, Beluga, Osetra and Sevruga. Beluga is the largest, softest, most expensive caviar. It is buttery and mild. Osetra is medium sized eggs, and Sevruga the smallest. Due to overfishing and poor relations with countries like Iran, it is near impossible to get caviar from the Caspian or Black Sea in the States. There are fish farms that produce good quality caviar from the White sturgeon in places like California.
There are also types of caviar, which include malossol-(lightly salted, Russian,) salted, pressed and pasteurized. My crab boat captain, Dennis, was kind enough to give me this as a present after a lucrative fishing season. It is a Russian Osetra (I didn’t ask how he procured it):
The Best Fish And Seafood Website In The World 