title: Emacs: font-lock explanation
body: <p>I'm using Emacs since a long time and I've customized it quite a lot.  I've even written simple ELisp functions and now I'm starting to use macros more and more.  I'm not anywhere near a knowledgable Emacs user but I'm not either a complete beginner.</p>
  
  <p>I'm using nxhtml, mumamo, dired, ido, custom keybindings and so many things I added throughout the years that I don't remember all of them ; )</p>
  
  <p>But there's something I really never understood: what is the "font-lock" mode and why should I care?</p>
  
  <p>For example, I've read that nxhtml and nxml, if I recall correctly, do not use font-locking.  Maybe I didn't understand that part well but in either way: what does it change for me, as a user?</p>
  
  <p>Or take for example this description about <em>WhiteSpace</em>:</p>
  
  <blockquote>
    <p>Note that when WhiteSpace is turned on, WhiteSpace saves the
    font-lock state, that is, if font-lock is on or off. And WhiteSpace
    restores the font-lock state when it is turned off. So, if WhiteSpace
    is turned on and font-lock is off, WhiteSpace also turns on the
    font-lock to highlight blanks, but the font-lock will be turned off
    when WhiteSpace is turned off. Thus, turn on font-lock before
    WhiteSpace is on, if you want that font-lock continues on after
    WhiteSpace is turned off.</p>
  </blockquote>
  
  <p>OK, fine.  I understand that.  But what does it change if font-lock continues after or not?</p>
  
  <p>Basically I just don't "get it", no matter how much I read about the subject.</p>
  
  <p>Any example/explanation as to what "font-lock" is under Emacs and why it concerns me would be most welcome!</p>