Shrimp are small, swimming crustaceans. There are shrimp both in fresh water and in salt water. They are in the infraorder Caridea. They are related to the prawns. The gills help to tell shrimp and prawn apart. Many prawns are called shrimp, and many shrimp are called prawns. In the context of cooking, the criterion is often only the size of the animal (prawn are bigger).
Many shrimp species are caught to be eaten. Usually, the head, and the digestive tract are removed before the shrimp is eaten.