The term Satan (Hebrew: ha-Satan; Persian: sheytân; Arabic: al-Shaitan ) is a personification of antagonism which has traditionally been associated with the three Abrahamic religions Judaism, Christianity and Islamic belief. In Judeo-Christian belief Satan is an angel known as 'the accuser' and a Jinn 'the adversary' in Islamic belief. Further both terms were orininally, used as a title for numerous entities that challenged the religious faith of humans in the Hebrew Bible. Since then, the Abrahamic religions have used 'Satan' as a name for The Devil.
Nevertheless, 'ha-satan' of the Old Testament (particularly the Book of Job) and 'Satan' of the New Testament are different entities. Also in Islamic belief, The Devil is known as Iblis. For more information on the different notions about Satan, The Devil and Iblis visit Wikipedia to read the various articles on these concepts.