Short answers, pulled from the story.
In the Hebrew Bible, ha-satan is a heavenly prosecutor and subordinate to Yahweh, not an evil cosmic adversary. The word, with the definite article, appears seventeen times in the Masoretic Text, restricted to two books: Job and Zechariah. He tests the loyalty of the righteous and accuses the nation of Judah in the heavenly court.
The transformation occurred during the Second Temple period, when Jewish communities lived under the Achaemenid Empire and came into contact with Zoroastrianism. The Zoroastrian spirit Angra Mainyu, a purely evil figure in cosmic opposition to good, influenced Jewish conceptions of Satan. Texts such as the Book of Enoch and the Book of Jubilees, written around 150 BC, developed Satan into an independent malevolent entity commanding demons.
Iblis is the Quranic name for Satan, probably derived from the Greek word diabolos. He was expelled from Paradise because he refused to bow before the newly created Adam, claiming superiority on the grounds that he was made of fire while Adam was made of clay. Thereafter, his sole mission became to lead humanity astray through evil suggestions called waswas.
Satan's appearance is not described in the Bible. By the ninth century, Christian art depicted him with cloven hooves, hairy legs, a goat's tail, horns, a flat nose, and a beard. His pitchfork was adapted from the trident of the Greek god Poseidon, his flame-like hair from the Egyptian god Bes, and his goat-legged form from the Greek deity Pan.
According to a 2013 YouGov poll, fifty-seven percent of people in the United States believe in a literal Devil. Fifty-one percent of Americans also believe that Satan has the power to possess people. By comparison, only eighteen percent of people in Britain hold the same belief in a literal Devil.
LaVeyan Satanism, practiced by the Church of Satan, treats Satan not as a literal supernatural being but as a symbol of individual liberty, human emotion, and opposition to spiritual belief systems that restrict personal freedom. Peter H. Gilmore, the High Priest of the Church of Satan, has described Satan as "a symbol of Man living as his prideful, carnal nature dictates" and as "a reservoir of power inside each human to be tapped at will".