What is Orientalism? What aspects of colonialism inspired Orientalism?

What is Orientalism? What aspects of colonialism inspired Orientalism? How has it affected art, both in terms of how the subject matter was portrayed by the artist and in the ways the work has been viewed? When discussing how the works are viewed take into consideration how artist wanted their works viewed, how the art was actually viewed when it was created, and finally how we, as modern viewers see it?