The later prophets are what we normally think of as prophets.  They stood out against authority and asked people to reform their ways to that of Yahweh, their God.  They were writing prophets, as opposed to the early prophets who did not write, but were written about.  These later prophets are normally divided into the three major prophets and the twelve Minor Prophets.  There were three famous major writing prophets whose works are very long.  Isaiah lived in the 8^th century BCE, but his work was not finished until around the 6^th century BCE.  On the other hand, Jeremiah and Ezekiel were 6^th century BCE prophetic writers around the time of the Babylonian Exile.