Originally Posted by From Wikipedia

Historically, sunroofs have been opaque and open to the air to allow the sun to shine directly into the vehicle, while moonroofs have generally been transparent or semi-transparent and designed to remain closed while allowing muted light to penetrate the vehicle.

The term moonroof has also been applied to sunroofs that can only tilt to provide additional ventilation. Those models that allow for complete retraction of the glass, either on tracks or into the automobile body itself, are now generally been accepted as the true sunroof.

Variations have become the norm and often combine the features of the Sun and Moon types into a single device. It is not uncommon to see tinted glass that can retract fully like a traditional sun roof, remain closed like a traditional moon roof, or tilt to allow for airflow.