title: MongoEngine: EmbeddedDocument v/s. ReferenceField
body: <p><code>EmbeddedDocument</code> will allow to store a document inside another document, while <code>RefereneField</code> just stores it's reference. But, they're achieving a similar goal. Do they have specific use cases?</p>
  
  <p>PS: 
  There's already a <a href="https://stackoverflow.com/questions/17454246/what-is-the-difference-between-embeddeddocumentfield-and-referencefield-in-mongo">question</a> on SO, but no good answers.</p>