Term generally used used to show appreciation to someone after they have done a deed for you.
It can also be used as a sarcastic way of saying "thank you" to someone after they have done something that you don't like, or that inconviences you in anyway.
Mike: Here goes that five bucks I owed you from yesterday.
Chris: Appreiciate you.
Sara: Matt, I think I gave you herpes.
Matt: Thanks a alot bitch. Appreciate you.