The difference between "Hunger" and "Appetite"
According to the website "Appetite vs. hunger", the difference is very similar to what you were saying:


  Hunger is the need to eat.


Hunger is instinctive, it is the body's way of letting you know it needs sustenance.

and 


  Appetite is the desire to eat.


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)