JOEL - The word "prophet" comes from the Greek prophetes, which means "inspired teacher." By scriptural definition, a prophet is anyone who has a testimony of Jesus Christ and is moved by the Holy Ghost (Rev. 19:10) to teach through inspiration. So prophecy can be considered to mean inspired teachings. President Wilford Woodruff said of Brigham Young to a congregation:

"He is a prophet, I am a prophet, you are, and anybody is a prophet who has the testimony of Jesus Christ, for that is the spirit of prophecy" (Journal of Discourses 13:165)

The gift of prophecy is a special spiritual gift that is available to every worthy member of the Church. Elder Bruce R. McConkie has said:

"Every member of the Church - acting in submission to the laws and system which the Lord has ordained - is expected to have the gift of prophecy. It is by this gift that a testimony of the truth comes." (Mormon Doctrine, Salt Lake City: Bookcraft, 1958, p. 542.)

Elder James E. Talmage of the Quorum of the Twelve wrote:
"No special ordination in the Priesthood is essential to man’s receiving the gift of prophecy. This gift may be possessed by women also." (Articles of Faith, 12th ed., Salt Lake City: The Church of Jesus Christ of Latter-day Saints, 1924, pp. 228-29.)

So whatever we learn or teach in the Church comes by way of prophecy. One of our articles of faith says:
"We believe that a man must be called of God, by prophecy, and by the laying on of hands by those who are in authority, to preach the Gospel and administer in the ordinances thereof." (A of F #5)

Church leaders who call other members to serve in the Church use the gift of prophecy to know who is going to be the right person for a particular position or calling.
Even though we are all entitled to the gift of prophecy, the senior prophet and president of the Church today is the only prophet who can receive revelation for the entire Church, with the sustaining support of the other Apostles and church members. The president of the Church and Apostles give us prophecy twice a year at every General Conference as we listen to their inspired teachings.
I assume that perhaps you might be refering to the ability of a prophet to see and or predict future events such as in the writings of Isaiah, Jeremiah, Amos, or my favorite, Joel :-), or even Christ Himself. That is actually a very small part of what a prophet does.
Elder James E Talmage said that "the function of prediction, often regarded as the sole essential of prophecy, is but one among many characteristics of this divinely given power. The prophet may have as much concern with the past as with the present or the future; he may use his gift in teaching through the experience of preceding events as in foretelling occurrences." (Articles of Faith, James E. Talmage, p. 228.)
Most prophecies that involve predicting future events that the world needs to hear, have already been given to us by those prophets of the Bible or by Christ or Joseph Smith; we don't really need to have much more than what has already been said by them.
I have often heard President Hinckley tell us things that he might not proclaim as a prophecy, but are nevertheless important information we need to know and prepare for about the future. For example, speaking of the need to prepare for coming the hardships the world will experience, he promised:

"I am not predicting years of famine in the future. But I am suggesting that the time has come to get our houses in order.
If you have paid your debts, if you have a reserve, even though it be small, then should storms howl about your head, you will have shelter for your wives and children and peace in your hearts." (Ensign, November 1998, pages 53-54.)

Our current prophets often direct more specific prophecies to certain groups within the church or to individuals. For example, the Apostle Henry B. Eyring came to our stake for a conference a few years ago, and in front of a congregation of stake leaders said,
"Well I'm supposed to be a prophet, so I am going to make a prophecy for this stake. I have been praying about this and have been inspired to tell you that the missionary work in this area, performed by both you and the full-time missionaries is going to greatly increase the number of convert baptisms within the next year."
The next year the number of converts in our stake more than doubled, and we didn't really change anything that we were already doing.

A prophet can not only have visions of the future, but can also recognize when a previous prophecy has been fulfilled. President Brigham Young once made the following prophecy about Utah:
"We will extend our settlements to the east and west, to the north and to the south, and we will build towns and cities by the hundreds, and thousands of the Saints will gather in from the nations of the earth. This will become the great highway of the nations.
Kings and emperors and the noble and wise of the earth will visit us here" (in Preston Nibley, Brigham Young: The Man and His Work [1936], 128).
Besides the obvious fulfillment of the prophecy of expansion and growth, President Hinckley identified the fulfilment of another part of that prophecy. He remarked that during the Olympic games he had met with presidents, ambassadors and leaders of all kinds. He pointed out that Brigham Young predicted this would happen more than 150 years before.
"We have witnessed the fulfillment of that prophecy in recent days,". (Gordon B. Hinckley, "The Church Goes Forward," Ensign, May 2002, 4).