As far as I aware what we call prawns are your shrimps. What we call shrimps may well be slightly different because they are smaller and normally brown and you eat the skins because they are too fiddly to peel.
Here is info on them indeed they do seem different but in common speech I think most people interchange them and probably get them muddled. I suspect that we are probably both guilty of getting the differences wrong and it has become easier to refer to all types in the UK as prawns and shrimps in the States.
http://www.pznow.co.uk/marine/decopoda.htmlThat clarifies things a bit. Also found a site which listed Prawns as a freshwater crustacean and Shrimp as a saltwater crustacean.
We do NOT eat the skins!:) I worked in a seafood restaurant for a couple of years while in High School. Spent every tuesday of the summer peeling and deveining about 20 lbs of raw shrimp.