what is android.R.layout.simple_list_item_1?

In all the examples I've seen they just use "android.R.layout.simple_list_item_1" when creating an ArrayAdapter. What is android.R.layout.simple_list_item_1,Is it just the name of a layout file called simple_list_item_1.xml or is it the id of the TextView required for the array adapter?

How do I see the content of the file or use my own file from my res folder?

public class MyClass extends ListActivity {
private String[] titles = {"Test"};

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.mylayout);

    setListAdapter(new ArrayAdapter<String>(this,
            android.R.layout.simple_list_item_1, titles));
     updateList();
}
}