title: What's the difference between DbContext and ObjectContext
body: <p>From <code>MSDN</code>:</p>
  
  <blockquote>
    <p>Represents a combination of the Unit-Of-Work and Repository patterns and enables you to query a database and group together changes that will then be written back to the store as a unit. <code>DbContext</code> is conceptually similar to <code>ObjectContext</code>.</p>
  </blockquote>
  
  <p>I though <code>DbContext</code> only handle the connection to the DB and the number of threads working against the DB. </p>
  
  <p>Now I understand it contains the tracking mechanism? I thought this was in the <code>ObjectContext</code>.</p>
  
  <p>So what is (in plain English) the difference between them?</p>