Those who are called to be prophets in the church have special duties to perform. It is not everyone who prophesies that can perform all these roles but those who are called to be prophets do.
They confirm God's guidance (Acts 13:1-4).
They declare openly, by inspiration, words from God without fear of position (Acts 21:8-11).
They exhort, edify and comfort (1Corinthians 14:1-3).
They convict believers and turn them to Christ (1Corinthians 14:24-25; 2Kings 17:13)