What is the black art and why dr. faustus decided or liked this art?

The black arts are those which study "black magic" and they represent a world that Faustus has never investigated.  He considers all that he has already achieved and seems to believe that nothing in that realm is "real" for him so he wants to move on.  He believes that even a study of theology only ends in Death, so he wants to study that which is "evil" which is what the black arts really represent.