title: part and export - What is the usage in dart?
body: <p>I am a beginner in Dart and Flutter. I have seen lots of examples on GitHub using part and export keywords. I have searched on google, but still don't understand it clearly. I already read the answer <a href="https://stackoverflow.com/questions/27763378/when-to-use-part-part-of-versus-import-export-in-dart">When to use part/part of versus import/export in Dart?</a></p>
  <p>still, I don't get it. Maybe it bit of a lengthy one and I am not a native English speaker.</p>
  <ol>
  <li>why are these keywords using?</li>
  <li>What they do?</li>
  </ol>