title: Magento cron_expr and cronjob
body: <p>I don't understand why I have to setup cron to run magento/cron.php and also have to config the cron_expr.</p>
  
  <pre><code>*/5 * * * * /absolute/path/to/bin/php -f /absolute/path/to/magento/cron.php
  </code></pre>
  
  <hr>
  
  <pre><code>&lt;module&gt;
    &lt;schedule&gt;
        &lt;cron_expr&gt;*/5 * * * *&lt;/cron_expr&gt;
     &lt;/schedule&gt;
     &lt;run&gt;
        &lt;model&gt;module/observer::myMethod&lt;/model&gt;
     &lt;/run&gt;
  &lt;/module&gt;
  </code></pre>
  
  <p>I think if we can magento/cron.php periodically then it is enough to run the method myMethod periodcally. Why we have to setup cron_expr? Sorry for my ignorance.</p>