It's usually a bit more involved, and expensive, to fly a person out for a job position than it is to invite someone to a resident/fellowship interview on their own dollar. Flight, decent hotel (possibly 2 nights), dinner, in some cases a tour of the city and meeting a real-estate agent, etc. In my relatively limited experience almost -every- potential employer wants to have a telephone chat with you before getting into that kind of time and financial commitment.
That said, my experience in those chats was basically the same as the actual interview -- cautiously/professionally casual, some questions about your background, why you're interested in that institution/location, do you have any hobbies, do you have any questions (you should come up with some beforehand -- little says "eh" more than having no questions; say so if they answered your questions during the chit-chat), etc., and a lot of feeling out personality similarities & differences. IMO you can ask pretty much anything about the job, though I usually save salary questions for late in the process; they probably want to feel like you're interested or not regardless of the pay, even if it may be the only thing on your mind.
