The navigation bar (at the bottom of the screen) can be transparent. Here is the way to achieve it.

<style name="AppTheme" parent="Theme.AppCompat">
    <item name="android:windowTranslucentNavigation">true</item>
</style>

The Status Bar (top of the screen) can be made transparent, by applying this attribute to the style:

<style name="AppTheme" parent="Theme.AppCompat">
    <item name="android:windowTranslucentStatus">true</item>
</style>