The LDS Guide to the scriptures states that a Mormon prophet is
A person who has been called by and speaks for God. As a messenger of God, a prophet receives commandments, prophecies, and revelations from God. His responsibility is to make known God’s will and true character to mankind and to show the meaning of his dealings with them. A prophet denounces sin and foretells its consequences. He is a preacher of righteousness. On occasion, prophets may be inspired to foretell the future for the benefit of mankind. His primary responsibility, however, is to bear witness of Christ. The President of The Church of Jesus Christ of Latter-day Saints is God’s prophet on earth today. Members of the First Presidency and the Twelve Apostles are sustained as prophets, seers, and revelators.
The Mormon prophet is a unifying leader of the Church. He is revered as a man in high standing with God who has much responsibility and authority. For this reason when a prophet enters or leaves a meeting, the entire congregation stands.
When the Mormon prophet speaks, his counsel is seen as coming from the Lord. This is found in Doctrine and Covenants 21:4-6,
Wherefore, meaning the church, thou shalt give heed unto all his [the prophets] words and commandments which he shall give unto you as he receiveth them, walking in all holiness before me; For his word ye shall receive, as if from mine own mouth, in all patience and faith. For by doing these things the gates of hell shall not prevail against you; yea, and the Lord God will disperse the powers of darkness from before you, and cause the heavens to shake for your good, and his name’s glory.
Members are encouraged to follow the prophet’s counsel, but not blindly. Members are asked to pray to receive personal confirmation that what the prophet has said is true.