We refer to the President of the Church as a "prophet, seer, and revelator". Each of those have a little different connotation. The main idea is that the President is the Presiding High Priest for the entire church. He receives revelation from God to guide the church and the members (or non-members for that matter). His revelations may not be prophesies in the sense of predicting the future. His revelations also may not be doctrinal, such as establishing the nature of the Godhead, etc. Most of the revelations are to guide the church and guide the members through the troubled water and times in which we live. Also, a very important, in my opinion the most important role of those we consider prophets, seers, and revelators is to be special witness of Christ to the world. This means that the resurrected Lord has revealed himself to them and they are equally qualified with the ancient apostles to bear testimony to the world, based on perfect knowledge, more than faith, belief, or hope, or a strong conviction, but a perfect knowledge, as sure as they know anything, that Jesus Christ lives, is resurrected, and stands at the head of His church today.
When you listen to fifteen men (First Presidency and the Twelve Apostles) each of whom are intelligent, sincere, and good men, each bear independent testimony that through experience "too sacred to give utterance" that they have a perfect knowledge of the resurrected Lord, by revelation, it's a powerful testimony. One who pays close attention to what they say can conclude they are telling the truth, they are lying, or they are deceived. If you know them for who they are, you quickly throw out lying. If you consider their intelligence, competence, sincerity, humility, goodness, integrity, the Christian values they possess, and the fact they they each make the claims of revelation independent of one another, you can also determine that being deceived by Satan is a not conceivable. That leaves telling the truth. Think about it. You might be surprised what you would learn, if you would carefully study the words of the living prophets and apostles as they bear apostolic testimony of the risen Lord. Their witnesses, combined with my personal study, reflection, and spiritual answers to prayer give me a rock solid conviction that prophets walk the earth again. Were living in a day. as if we were in the days of and in the midst of Peter, James, John, and the others. It's great to be a part of it. I wish all Christians and all people everywhere could see it.