title: Difference between Iterator and Iterable
body: <p>What is the difference between Iterator and Iterable? Is one sub-type of the other or not? What are the actual differences in some real applications?</p>
  
  <p>I am trying to read some tutorials and specifications, but they are all very complicated.</p>
  
  <p>(I am using ES6 and Babel, if that helps.)</p>