title: Difference Aggregate Root/Entity
body: <p>I' struggling with this question : how to tel if a concept is an aggregate root or just an entity (that is part of an AR) ? :</p>
  
  <ul>
  <li>They both got Ids</li>
  <li>They both are composed by entities or value object</li>
  </ul>
  
  <p>Maybe if I need to reference an entity in an other AR then I need to make it an AR : if somewhere on the app I need to link something to a particular order line, then order line will become an AR.</p>
  
  <p>Or it's just in terms of lifecycle, but if it is, I don't see the point of having an entity inside an AR : it's just value object.</p>
  
  <p>Or maybe it's because an entity can change of AR then I'll promote it as AR.</p>