Today the Church has at its head Jesus Christ. His spokesman is the Prophet, who is also the President of the Church on Earth. He acts in God's name and proclaims or warns or reassures what Heavenly Father would have us know. The Prophet holds all of the keys of the Priesthood. He has delegated these keys to the Savior's 14 Apostles (2 of them being in the First Presidency as counselors to the Prophet and President).
The organization continues down with Priesthood holders known as Seventies. Above them the Quorum of 12 has 12 men. In a quorum of 70, there are 70 men. Today we have 7 quorums of 70--because we are a worldwide Church and we need the leadership throughout the world to help with the 15 million+ members.
Below the quorum of 70 we have our stakes--geographic boundaries of give or take 7-9 geogprahic boundary-determined congregations (called wards). There is a stake president and his counselors who lead a stake, and they have high councilmen to assist in their work. At the head of a ward is a bishop (or a pastor) and his counselors. Within wards (and branches, which are congregations that do not have enough Priesthood leadership to function as a ward), one will find high priests, evangelists (otherwise known as teachers and missionaries), priests, teachers, and deacons. These various positions within the Priesthood work hand-in-hand with all other positions in the Church. Nothing can be done or operated without the Priesthood in the Church, but remember that there would be no need or point of the Priesthood if all of us were not a part of the Church and a part of the workings of it.