Raw fish eggs are also called roe. When they are salted and processed, they are generally called caviar. However, in the United States, only processed roe from sturgeon and paddlefish can be labeled as caviar.
Anything that is labeled only "caviar" is from some type of sturgeon, which is an endangered species. Other types of caviar must have the fish they come from preceding the word, such as "paddlefish caviar." Caviar is considered a luxury item, but some roes, such as salmon or trout, are cheap enough to buy and eat without breaking the bank. Salmon roe is large and orange and has a distinct pop when bitten.