what does android.R.layout do? An overview
<p>Im trying to get an overview of what  android.R.layout does in an android project.</p>

<p>From the spinner tut at <a href="http://developer.android.com/resources/samples/Spinner/index.html" rel="nofollow">http://developer.android.com/resources/samples/Spinner/index.html</a></p>

<pre><code> this.mAdapter = ArrayAdapter.createFromResource(this, R.array.Planets,
                android.R.layout.simple_spinner_dropdown_item);
</code></pre>

<p>I can see a private member</p>

<pre><code>public static final int simple_spinner_dropdown_item
</code></pre>

<p>But what is this?</p>
