Smooth! - Jazz that's easy and in background. Always welcome if you consider to throw a party and want the guests to be able to talk to each other.
Smooth
What is Smooth Jazz? - The answer is hard to find. Well, it's something between Jazz and Lounge but where are the borders between these musical styles / genres? I would say there are no borders and you cannot clearly seperate one style from another. In particular. What is Jazz? - It's a very wide definition of a certain kind of music. You may end up with this discussion finding out, that this is very senseless since good music is good music and nothing else matters.