Most Christians reserve the word "devil" for Satan (literally
"the adversary"), and demons are his minions. The Revelation of
St. John tells us that a third of the host of heaven followed
Lucifer / Satan. However, the New Testament uses the word
"devil" in a more general manner, almost how we currently use
"demon" (eg. an evil spirit). In fact, the Joao Ferreira de
Almeida translation (Portuguese) uses the word "demonio"
("demon"). From where I see things, devil is the exact adversary
of God. Devil is otherwise called Satan. Demons are those
entities those are "negative" or "harmful" in nature. From the
stand point of most Eastern philosophies, we do not have a
"satan" or "devil" as the central controller of negative forces
because as we see and experience, demons are creation of God as
well. It is upto each one of us, with the wise use of choice to
harness the "good" power of God and overcome the "demonic'. Moon
has correctly explained the views of Christianity. The devil and
his demons play opposite to God