title: In docker technology, what is "container format", and what is it used for to do?
body: <p>The docker docs only said:</p>
  
  <blockquote>
    <p>Docker Engine combines the namespaces, control groups, and UnionFS into a wrapper called a container format. The default container format is libcontainer. In the future, Docker may support other container formats by integrating with technologies such as BSD Jails or Solaris Zones.</p>
  </blockquote>
  
  <p>But I still can not get what is really "container format".</p>
  
  <p>Can someone give me more detailed information about "container format"？And what can I do with "container format"? </p>
  
  <p>Thanks.</p>