The Hebrew Bible, or Tanakh, is the Bible of the Jewish people, and the basis of the Christian Old Testament. Classically, it is divided into 3 parts.
The Pentateuch, the 5 books of Moses (from Genesis through Deuteronomy) were canonized earliest, and set in place by 450 BCE (before the Common Era, also called BC, Before Christ).
The Prophets were largely canonized by about 300 BCE.
The Writings (the rest of the Hebrew Bible) were canonized within 100 years after the Common Era (CE, called AD (Anno Domini) by the Christians.
The canonization was done by Jewish scholars who can be seen as the precursors of the rabbis. Their classical religious belief was that the Pentateuch was dictated by God to Moses, and that each of the other books was divinely inspired by God to its author, but not dictated. These redactors or compilers chose which books to include, and chose the order they were placed in (generally but not entirely chronological), but did not change the contents of any text.
The Catholic Church created it's version of the Old Testament using theTanakh plus some Jewish writings that were never in Hebrew, or no longer existed in Hebrew at the time of canonization, called the Apocrypha. And they changed the order of some of the books. The Protestant churches removed the writings of the Apocrypha, feeling writings not in Hebrew were less likely to be authentic. The result is that the contents of the Hebrew Tanakh used in Judiasm today and the contents of the Protestant Old Testament are the same, but the books are not in the same order.
(My wife, KrisL, a professor of Jewish Studies, confirmed we got this right.)