lol!you need to have a good listenin mode (not hearing mode)...for both of them ...
and if practised it becomes a SKILL!
Interpersonal has more to do with the type of relationship you have with a person in context of a longer term. How you act and react to them over time, through different situations, etc.
Communication skills is just about how well you can represent what you are thinking so that others understand you. Here's a cute quote for you on this subject:
"I am responsible for what I say. I am not responsible for what you understand." :)