Relative dating is used commonly when looking at the relative order of geological events.
Accurate dates also allow us to create sequences of evolutionary change and work out when species appeared or became extinct. These are: Where possible, several different methods are used and each method is repeated to confirm the results obtained and improve accuracy.
Before radiometric dating (or other methods of absolute dating like counting tree rings) it was difficult to determine the actual age of an object.
Radiometric dating, based on known rates of decay of radioactive isotopes in objects, allows a specific age of an object to be determined to some degree of accuracy.
We can absolute date materials but it will always have an uncertainty range, we can never know the age with infinite precision.
Relative dating is like looking at a multi-layered cake.