What is a virtualenv, and why should I use one? : <p>I am trying to install a Python package with this command</p>

<pre><code>pip install &lt;name of package&gt;
</code></pre>

<p>I'm getting permission errors and I'm not sure why.  I could run it with <code>sudo</code>, but someone told me that was a bad idea, and I should use a virtualenv instead.</p>

<p>What is a virtualenv?  What does it do for me?</p>
