Shrimp and Prawns, although look similar to each other are very different in anatomy. Similar in taste.
Prawns are generally larger in size and there are less of them in the ocean. They also have small claws and larger legs when shrimp do not. They both stay close to the ocean floor which means groupings of them can be huge if found.
Prawns are considerably more expensive and you get less per pound do to the size and quantity. These two are used highly in Southern America cuisine, Gumbo and south comfort seafood dishes due the closeness to the Gulf of Mexico.
Around the world these two are used as much if not more than other crustaceans. Paired with white wine and pasta/rice dishes, make them very simple to cook.