Who is satan?

People's beliefs of Satan range from the silly to the abstract: from a little red guy with horns who sits on your shoulder urging you to sin, to an expression used to describe the personification of evil. The Bible, however, gives us a clear portrayal of who Satan is, and how he affects our lives. Put simply, the Bible defines Satan as an angelic being who fell from his position in heaven due to sin and is now diametrically opposed to God, doing all in his power to thwart God's purposes for humanity.