title: The android:name attribute in the <fragment>
body: <p>Please explain <code>ArticleListFragment</code> and <code>ArticleReaderFragmet</code> as they are in this code:</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
      android:orientation="horizontal"
      android:layout_width="match_parent"
      android:layout_height="match_parent"&gt;
      &lt;fragment android:name="com.example.news.ArticleListFragment"
              android:id="@+id/list"
              android:layout_weight="1"
              android:layout_width="0dp"
              android:layout_height="match_parent" /&gt;
      &lt;fragment android:name="com.example.news.ArticleReaderFragment"
              android:id="@+id/viewer"
              android:layout_weight="2"
              android:layout_width="0dp"
              android:layout_height="match_parent" /&gt;
  &lt;/LinearLayout&gt;
  </code></pre>
  
  <p>I don't know what they refer to? Is it either the Fragment class (or its subclass) that use in source code or XML files for layout?</p>
  
  <p>If they are XML files where must they be located?</p>