title: What goes in /var?
body: <p>I read <a href="http://linuxcommand.org/" rel="noreferrer">The Linux Command Line</a> by William Shotts, and there are some descriptions of Linux files (system directories):</p>
  <blockquote>
  <p>The <code>/var</code> directory contents don't change. This tree is where data that is likely to change is stored. Various databases, spool files, user mail, etc. are located here.</p>
  </blockquote>
  <p>I am wondering: If the <code>/var</code> directory contents are not supposed to change, why is there a <code>www</code> directory in <code>/var/www</code> after installing <code>apache-php</code>?</p>
  <p>The <code>/var/www</code> directory is where we must edit, create or delete files. This is a localhost public directory.</p>
  <p>Why did he say, that the <code>/var</code> directory contents don't change?</p>