title: what does "domain" and "persistence" mean?
body: <p>I always encounter these 2 words.</p>
  
  <p>I know that when you are talking about domain model you are talking about objects.</p>
  
  <p>And persistence layer is a layer you store your data, eg. MySQL database.</p>
  
  <p>But could someone explain these words more thoroughly?</p>
  
  <p>Why is it called domain? Why persistence?</p>
  
  <p>Thanks!</p>