Shrimp are small crustaceans that are generally sold fresh in the shell with the heads already removed. They are also available shelled and cooked or frozen. Shrimp are marketed in a variety of sizes-small, medium, large, and jumbo. Before cooking, shrimp are usually peeled and their thin, vein-like intestinal tracts removed.
To peel and devein shrimp:
Using your thumbs, split open the thin shell along the concave side, between the two rows of legs. Peel the shell away. Using a small knife, make a shallow slit along the back to expose the dark, veinlike intestinal tract. With a knife tip or your fingers, lift up the vein and discard.For other shellfish varieties, see clams, crabs, lobster, mussels, oysters, and scallops.