kozak - if you give some idea of where you live & fish, it will be lots easier to try and figure out what sort of fish.
Note that 'river carp' are simply carp that live in a river rather than a lake.
Take a look at this
web site to get more info on the usual species that are often just called "carp". The web site is in Iowa but they cover the main species you will find in the US.
Common carp (Cyprinus carpio) are mainly what the UK folks fish for. Easy to spot since they body shape is unusual and Cyprinus carpio have whiskers (smaller than those on a catfish though). If you see talk on here about Mirror carp and Leather carp, they are Cyprinus carpio but with very different scale patterns. We do have some mirror carp but in most places they are really rare.
" My choices in life were either to be a piano player in a whore house or a politician. And to tell the truth, there's hardly any difference!" - Harry Truman, 33rd US President