In fact, "oyster" and "raw oyster" are strictly oysters, and there is no difference at all. Generally, the north is called "sea oyster", while the south seems to be called "raw oyster". For example, the food stalls outside our community are like this. If I order two dozen "sea oysters" from my boss, he will probably look at me blankly and ask, "What is the sea?" .
However, apart from the different names of oysters in different areas in the north and south, there are too many varieties of oysters, and as many as a dozen or twenty kinds can be seen. What's more, the shape and appearance of oysters will change with the growth environment, so it is difficult for ordinary consumers to distinguish which kind of oysters are in front of them, and many people in this industry can't distinguish all oysters. So now people in some places seem to be "established". The big oyster is called "oyster" and the small oyster is called "sea oyster".
So some people say that "oysters" are "sea oysters", which is actually no problem to discuss because they are the same species. But in the vegetable market, if the ingredients are named according to the convention, it may be a bit different. For example, if you want to buy a relatively large, high-quality and expensive "oyster", and the other party receives the corresponding money, but sells you a relatively small and cheap "oyster" and then says "all oysters are the same", this is not kind. Just like when we buy hairy crabs, 22 1 and 42 1 are China hairy crabs, but the prices are different. At this time, if the seller says, "Not all hairy crabs are the same." This is obviously unreasonable from the perspective of commodity trading.
So to sum up, "oyster" and "raw oyster" are oysters, and there is no difference. But because many people think that "oysters" are expensive and "sea oysters" are cheap, they are different in the sense of goods. It should be noted that this logical relationship is that it is expensive because of its good quality, and people give this good quality a name of "oyster" to show the difference, rather than being expensive because of adding a name of "oyster".