Oyster sauce vs Oyster-flavored sauce

Oyster Sauce mainly use Oyster Boiling into sauce. Oyster Flavored Sauce use food additive

The original oyster sauce was made simply by boiling oysters down until they made a browned, thick sauce. The oysters themselves sort of boiled into oblivion in the process. The best true oyster sauces are still made much that way- but it also makes them very expensive. Most modern oyster sauce is "flavored", meaning that an oyster flavor extract is added to a base sauce. In some cases, that flavoring will not actually come from a real oyster, but is a chemical mixture designed to mimic the taste. Those tend to be the less expensive options. Real oyster sauce tastes wonderfully complex, and isn't so hard to find in a good Oriental market. My favorite is Panda brand, followed closely by Lee Kum Kee. Lee Kum Kee was the original maker of the sauce, for what that's worth. You just need to look on the bottle to see if what you have is true oyster sauce or a flavored sauce