In certain fields(IM, peds) there won't be a difference. Your 'intern' year will really just be your first year of residency and you will spend much of the year in the same department as you will the next few. But in many specialties your intern year will be either a year of general medicine, a year of general surgery, or a mixture of both. There is a good chance this will be at a different hospital than where you will spend the next 3-4 years. For example, a person matching dermatology has to do a year of internal medicine first. That would be their intern year. Years 2-4 of their residency would be spent in dermatology.