title: How is `ls` work compare `*`?
body: <p>The result of <code>ls</code> is difference between <code>*</code>?
  For example:
  <code>ls | du -sh</code> 
  will only show one line for total size of current dir.
  <code>du -sh *</code> 
  will show the size of each file or subDir in current dir.</p>
  
  <p>why the result is not same? </p>