When I am "hungry", I need something to eat physically. But what about "appetite"? I think it is a psychological phenomenon. Is that correct?
According to the website "Appetite vs. hunger", the difference is very similar to what you were saying:
Hunger is instinctive, it is the body's way of letting you know it needs sustenance.
It is a coordination between the brain and the stomach, this is learned behaviour.
Some further information can be found in the article preview "The Biological Nature of Appetite" (Stellar, 1992)