Digi Pak

A digi pak is a 6 panel packaging for a CD or DVD. They usually include a gatefold style outer binding and a plastic tray to hold the CD/DVD within the case.
A digi pak is an alternative, modern version of the standard CD case, they usually hold more that one CD and tend to be used for 'deluxe' versions of albums.
They are also used for multi disc CDs, as they can hold more and give it a professional look and feel, especially when paired with artwork that matches the artist or CD.