The difference between oysters and sea oysters is mainly in size. Oysters are raised, which is relatively large, and the sea consumption is salvaged, which is relatively small. Oyster belongs to mollusca, bivalve and Pinctada. It is the largest cultured shellfish in the world, one of the important marine biological resources available to human beings and a globally distributed species. Oysters are not only delicious but also nutritious.

Oyster shells can be divided into three layers in section; The outermost layer is a thin and transparent stratum corneum, the thickest layer is a columnar structure composed of calcium carbonate called prismatic layer, and the inner layer is a flaky structure called nacre.

The oyster shell is secreted by the lower mantle, which extends from the top of the shell to the edge of the abdomen. It is a two-layer epithelial cell with connective tissue in the middle. There are muscle fibers in the membrane that make it adhere to the inner surface of the shell. The edge of the mantle thickens to form three folds, and there are radial muscles and annular muscles on the inner folds to make the edge close to the shell. There are a large number of sensory cells or organs in the folds, which have tactile and visual functions. The outer fold has a strong secretory function.