1 Corinthians 14

After teaching the Corinthians about the many gifts of the Spirit, Paul then follows with this instruction -

"I would that ye all spake with tongues, but rather that ye prophesied: for greater is he that prophesieth than he that speaketh with tongues, except he interpret, that the church may receive edifying." (New Testament 1 Corinthians 14:5)

Because -

"...he that prophesieth speaketh unto men to edification, and exhortation, and comfort." (New Testament 1 Corinthians 14:3)

For we are to -

"FOLLOW after charity, and desire spiritual gifts..." (New Testament 1 Corinthians 14:1)

For the purpose -

"...that ye may prophesy." (New Testament 1 Corinthians 14:1)

"...forasmuch as ye are zealous of spiritual gifts, seek that ye may excel to the edifying of the church." (New Testament 1 Corinthians 14:12)

What does Paul mean to "prophecy" that the Church or saints will be edified? John testifies -

"...I am thy fellowservant, and of thy brethren that have the testimony of Jesus: worship God: for the testimony of Jesus is the spirit of prophecy." (New Testament Revelation 19:10)

Elder John A Widstoe defined -

“...a prophet is a teacher. That is the essential meaning of the word. He teaches the body of truth, the gospel, revealed by the Lord to man; and under inspiration explains it to the understanding of the people. He is an expounder of truth. Moreover, he shows that the way to human happiness is through obedience to God’s law. He calls to repentance those who wander away from the truth. He becomes a warrior for the consummation of the Lord’s purposes with respect to the human family. The purpose of his life is to uphold the Lord’s plan of salvation. All this he does by close communion with the Lord, until he is ‘full of power by the spirit of the Lord." (Evidences and Reconciliations, pp. 257–58.)

He also explained -

A prophet is a teacher of known truth; a seer is a perceiver of hidden truth, a revelator is a bearer of new truth. In the widest sense, the one most commonly used, the title, prophet, includes the other titles and makes of the prophet, a teacher, perceiver, and bearer of truth." (Evidences and Reconciliations, pp. 258–59.)

But as John so testified, the know truth is the testimony of Jesus Christ, His doctrine, and His kingdom. Elder McConkie explained -

“...Prophets are simply members of a true Church who have testimonies of the truth and divinity of the work. They are the saints of God who have learned by the power of the Holy Ghost that Jesus is the Christ, the Son of the living God..." (The Promised Messiah, pp. 23)

Knowing this helps to explain Moses's desire -

"...would God that all the LORD's people were prophets, and that the LORD would put his spirit upon them!" (Old Testament Numbers 11:29)

This also helps to explain as Saul sent his servants to find David -

"...when they saw the company of the prophets prophesying, and Samuel standing as appointed over them, the Spirit of God was upon the messengers of Saul, and they also prophesied." (Old Testament 1 Samuel 19:20)

Which means they also bore testimony of Christ. This explains why Paul said to the Corinthians -

"Wherefore, brethren, covet to prophesy..." (New Testament 1 Corinthians 14:39)