title: What's the difference between 'operator' and 'method' in RxJS?
body: <p>While reading the document of RxJS, the word 'operator' is frequently used.</p>
  
  <blockquote>
    <p>We have already used the create and range operators in previous topics to create and return simple sequences. We have also used the fromEvent and fromEventPattern operators to convert existing events into observable sequences. </p>
  </blockquote>
  
  <p>Those so called 'operators' to me are just simple 'methods'.
  Is there any distinction between 'operator' and 'method'?</p>