Prawns are similar to shrimps but are (most of the time) considerably larger in size. The difference lies in their gill structure and they (prawns) have longer legs. You can also find out if what is served to you is a prawn or shrimp by looking at it's 2nd plate. On a shrimp the second plate overlaps both the first and third plates, but on a prawn the second plate will only overlap the third plate. For the most part, their looks and taste are very similar.