title: How to effectively use the self-documenting system of Emacs?
body: <p>I am a newbie on Emacs. I was going to learn how to close a buffer, so I typed <code>M-x</code> <code>apropos-documentation RET</code>  <code>close buffer</code>. Then I got a lot of useless information.</p>
  
  <p>Given the above senario, what's the right way to find what I wanna know using the self-documenting system?</p>
  
  <p>Or the self-documenting system is useless compared to Google in the modern day?</p>