God and Satan in the book of Job: how did they know about this conversation?

Job chapter 1 vers 6 - 12 talks about God and Satan having a conversation. Where does that story come from? Job does not know what is going on and I have never heard anyone talk about it. Is it a revelation or is it a tradition that helps us understand what was said in this conversation? Who knew and who was told that this conversation was going on? (If there is not another Bible verse that can explain this question maybe the RCC or the Orthodox church have a tradition that can explain such a question). The author is not as important; **how did the author know** is the important part.