Conventions of a Digipak

What is a digipak and how does it oppose to an album cover?

A digipak typically contains bonus features consisting usually of a tracklist, lyrics to a track, perhaps how the music video was made or information on the artist. It consists more than what an album cover would stereotypically entail. 

What do we usually find on the various faces of the digipak?

Blatantly, the front cover of the digipak would be an image of the artist, the name of the artist and the name of the album/digipak. This therefore provides enough information for a member of the public or possible consumer to identify the aspects of the album making it a quick and easy way to choose which product to buy. The back of the digipak is usually identified with a track listing of the CD whereby the order of the songs are listed alongside the names. Additionally, the other faces within the digipak may entail lyrics to one particular song within the CD or perhaps information of the artist or how the music video was made. On parts of the digipak usually the back, there will be a barcode, typically adjacent to it being a price of the digipak allowing a consumer to understand the price of the product. If the song was to contain explicit content, there may be identification of this aspect through the well known explicit content tag (as shown below.) 

Does there need to be a theme between the faces?
It is a necessity to have a theme following through the faces of the digipak as the audience needs to understand that they all relate and have a purpose of addressing the correct brand identity for the artist allowing it to appeal to the specific target demographic. There should be a link in fonts, imagery and colour schemes making sure it is aesthetically pleasing to a member of the audience making it stand out from other digipaks when put on a shelf.