"Whereabouts" is usually used in place of "where". It is asking for a more general location - as in what general areas you interested in or would like to mention, it is deliberately nonspecific. It is usually used informally and conversationally, not so much used when someone is asking for an itinerary or specific location. I would not expect this to be used by someone who expects a specific answer, unless their speech patterns tended towards the informal.
I would use "whereabouts" in a conversation to refer to plans that might be uncertain or still in the process of being narrowed down, or to avoid asking or offering specific information for whatever reason - perhaps to avoid the appearance of prying or being nosy for the person asking, or for answering to avoid giving specifics if someone is uncomfortable with prying, or planning something, or even being playful.