title: What is Object relational mapping(ORM) levels in hibernate
body: <p>I've came across this question a couple of times when searching for jobs, but, when developing, I never come across this terminology anywhere. I know they are 4 levels in it, but does it really matter for me to know what it is? As an application designer, should I know this? Can somebody explain this with real world scenarios? </p>
  
  <p>Thanks. </p>