A prophet can mean the same thing as a preacher. It can also refer to someone who has insight into the future or predicts future events, which are called prophecies.
Many books in the Old Testament were written by or about prophets and contain their messages for repentance or of predictions for future events. Many of these prophetic predictions anticipated Jesus, though some had a more current focus, while a few looked at the end times.
See the list of prophetic books in the Bible.
Key verse about Prophet: If what a prophet proclaims in the name of the Lord does not take place or come true, that is a message the Lord has not spoken. That prophet has spoken presumptuously, so do not be alarmed (Deuteronomy 18:22, NIV)
A lifelong student of the Bible, Peter DeHaan, PhD, wrote the 1,000-page website ABibleADay.com to encourage people to explore the Bible. His main blog and many books urge Christians to push past the status quo and reconsider how they practice their faith in every area of their lives.