Here in Job 1:6, The term Satan, (literally translated as “the accuser”) is preceded in Hebrew by the definite article (“the”). Thus, in the context of Job it appears to describe a function rather than serving as a proper name. Though the individual here, functioning as an adversary to Job, may well be the one who later bears the name Satan, the term does not clearly take on the role of the personal name, Satan, until the intertestamental period (specifically the second century BC).
The noun satan, occurs in nine contexts in the Hebrew Bible. In five of these contexts, it refers to human beings (1 Samuel 29:4, 1 Kings 11:14, 23, 25) - (See how this carries over into the New Testament in Mark 8:33 when Jesus addresses Peter as the "adversary" to His mission on earth) and in four it refers to celestial beings (Numbers 22:22, Job 1:6, Job 2:1, Zechariah 3:1). When it is used of human beings it is not a proper name, but rather a common noun meaning ‘adversary’ when used in a political or military sense, or ‘accuser’ when it is used in a legal context. In the celestial realm there is only one context in which satan might be a proper name. In the other three contexts it is a common noun, meaning ‘adversary’ or ‘accuser’.
The term satan is rendered as diabolos (Devil) in the Septuagint (Greek translation of the Hebrew Bible).
The New Testament shows a developing picture of Satan as an archenemy of God. Extra-biblical works written prior to and contemporary with the New Testament documents parallel this development. In the New Testament, the word “devil” is used 32 times, Satan is used 33 times, Belial once (2 Cor 6:15), and Beelzebul is used 7 times.
For more on Satan in the cultural context of the Biblical world, here are some helpful links:
Baker Encyclopedia of the Bible
Dictionary of Deities and Demons in the Bible
The Lexham Bible Dictionary
Connected study article: Job: A Commentary Style Study Part 2