The Church's faithful believe that the teachings of the Church are correct. From where does such belief originate? How can one know with confidence that Church teachings are true? The answer lies with the head of the the Catholic Church, the Pope, in unison with all the Bishops of the church. Together they form the teaching authority of the Church. The Pope and the Bishops act together to formulate teaching that the faithful can be assured is correct. This congregation of Pope and bishops form what is known in the Catholic community as the Magisterium.
The Magisterium has its basis for authority in Christ himself. Christ charged his diciples with spreading God's word. Christ assured them they would speak with the authority granted by God Himself: "He who hears you, hears me; he who rejects your rejects me, he who rejects me, rejects Him who sent me" (Luke 10:16). Through the ensuing centuries, the fathers of the Church have come to understand this charge which Jesus made allows them to speak with His authority. Guided by the Holy Spirit, the Church leaders speak without error. This is known as infallibility.
There are several different technical definitions of the Magisterium. The Extaordinary Magisterium refers to the Pope, in Unison with all of the Church's Bishops, making an official pronouncement of Church teaching. When the Pope and the Church's Bishops come to an agreement regarding specific doctrine without making an official pronouncement, they are conducting church authority as the Ordinary Universal Magisterium. When the Bishops return to thier own local diocese, they are charged with the obligation to teach their flock. The local Bishop teaches locally the infallible doctrine of the Church. The authority of the individual Bishop to teach the faithful of his diocese is known as the Ordinary Magisterium.
For about two-thousand years, the obligation to educate the faithful about Christ's teachings have fallen on the shoulders of the Church's leadership. The Bishops, in unison with the Pope, and inspired by the Holy Spirit, make definitive pronouncements regarding the teachings of the Church. Under such circumstances, the Bishops and Pope, speak without error. The faithful can be assured that these teachings made offical can be followed and instituted knowing that it is God Himself that teaches. Through the Magisterium, the faithful know that God's word is come from Him directly just as Jesus taught us those many centuries ago.
Notes:
For further reading, read the Church's official document:
Dei Verbum: Dogmatic Constitution on Divine Revelation.
It can be found on the Official Vatican website at:
http://www.vatican.va/archive/hist_councils/ii_vatican_council/documents/vat-ii_const_19651118_dei-verbum_en.html
A printable version can be found at:
http://www.ewtn.com/library/COUNCILS/V2REVEL.HTM
