The story of Job is interpreted in many different ways by theologians but my interpretation is that nobody knows why God lets Satan live and torment us. God is God and can do whatever He wants. Ours is not to question why, ours is but to do or die. Satan, being a spirit, is neither male nor female. However, like his Creator, Satan is usually referred to as a masculine being.
Possession is bodily invasion by the devil.
The Catholic Church still performs exorcisms on those considered to be possessed. Jesus is said to have cast out demons, i.e., performed exorcisms, and the Church considers itself to have been given this same power by Jesus. Throughout the centuries, many pious religious people have considered those with certain mental or physical illnesses to be possessed by Satan. More frequent than outright possession, however, has been the accusation of being in consort with the devil. Satan is believed to have many powers, among them the power to manifest himself in human or animal form.