G.B.
Like the others said an RN has a 2 year Associate's Degree while a BSN has a 4 yr Bachelor's degree. You can sit for boards with the 2 year degree and work, but know that many hospitals are starting to want you to complete the BSN within a certain amount of time after starting (if you start as an RN). I think it has to do with Magnet Status for the hospital.
ETA: Looking back at others answers, around here the hospitals pay the same for BSN as RN. Starting salary was exactly the same for the two (southwest Ohio).