In our everyday lives, we live, what we may call, a "life job description." Life Job descriptions are ways of identifying and characterizing what role we fill in the events of our society. For instance, we may have the title Dad, and with that title comes all sorts of expectations and "job" descriptions. It is how we can say, well A is a good dad, while B is a bad dad. These "life Job descriptions" define us within an understandable context in our culture.
So too with the prophets of the OT. Prophets in ancient Israel (and in the divided kingdom of Judah and Israel) fulfilled a "Life Job description" within their cultures.
However, the modern understanding of a prophet has tweaked the true Life Job description of those called prophets. In our time, when we think of the word Prophet, we often think of fortune tellers, or perhaps a better way to put it would be future tellers. That the Life Job description of the prophet was to tell the future. This is far from the truth- in fact the Bible specifically speaks against future telling, called in the Bible divination.
Nor is the Life Job description of the Prophet an oracle of the Greek and Roman mythologies. an oracle is defined as, "a priest or priestess acting as a medium through whom advice or prophecy was sought from the gods in classical antiquity."https://www.google.com/?gws_rd=ssl#q=define+oracle
Instead, the biblical Prophet Life Job description is best understood as:
1. A divinely instituted office (Duet 18:19-22)
2. A messenger, envoy, or ambassador for Yahweh
3. Covenant enforcers- in other words, reminding the people of God what promises they had made to God and why they needed to keep those promises*
So as you read the prophets, remember what that Life Job description really means
* Per Dr. David Dorsey, "The Prophets."