“An 'apostle' is an ordained leader in the Melchizedek Priesthood in The Church of Jesus Christ of Latter-day Saints. Apostles are chosen through inspiration by the President of the Church, sustained by the general membership of the Church, and ordained by the First Presidency and Quorum of the Twelve Apostles by the laying on of hands. . . . In addition to serving as witnesses of Jesus Christ to all the world (D&C 107:23), as Jesus' apostles did, members of the current Quorum of the Twelve Apostles hold the keys of the priesthood--that is, the rights of presidency (D&C 107:35; cf. 124:128)” (Encyclopedia of Mormonism , 1:59-60).
To continue reading about the role and description of Apostles, see the Encyclopedia of Mormonism, a joint product of Brigham Young University and Macmillan Publishing Company. (Its contents do not necessarily represent the official position of The Church of Jesus Christ of Latter-day Saints.)