Service in the Mormon Church is voluntary. Positions of service are known as callings, because people are “called” through revelation to those in authority over them. Essentially, the idea is that the Lord has called, or asked a person to perform a specific duty in the Mormon Church. For a calling to be seen as legitimate, it must be given by a person that has the authority to give it. For example, on the ward level, a bishop will give the call; on a stake level, the stake president will issue the call. Church-wide callings (such as mission president) come from the First Presidency.
The Lord requires our hearts and minds, and there is no calling that is above another, or more important than another. All are needed and are an important part of Christ’s Church. Some callings may come with more responsibility. For example, a bishop is responsible for the welfare of his entire ward (congregation), while a Relief Society President is responsible for only the women in the ward. But both of the positions are equally necessary to help to further Christ’s kingdom.
Nor is there necessarily a progression of prestige from calling to calling. For instance, the calling of bishop is a calling of great responsibility and demands a huge investment of time. Most men who are called as bishops have leadership ability and are living exemplary lives. Thus, there is some prestige attached to the calling. However, once a bishop is released from the calling, usually after 5 years, he might be called to teach a Primary class of young children during Sunday School. All callings in the Mormon Church are temporary, except those of the General Authorities—the Prophet, the Twelve Apostles, and First and Second Quorums of Seventy.