In Django, what does symmetrical=True do?
<p>For example:</p>

<pre><code>class Contact(models.Model):
    contacts = models.ManyToManyField('self', through='ContactRelationship', symmetrical=False)
</code></pre>

<p>What does the <code>symmetrical=False</code> parameter do?</p>

<p>When should it be left as <code>True</code>, and when should it be set as <code>False</code>?</p>

<p>How does this settings affect the database (does it create extra columns etc)?</p>