http://en.wikipedia.org/wiki/Infallibility_of_the_church
Infallibility in the Catholic Church
The Catholic Church teaches three sources of Infallible teachings: Sacred Tradition, Sacred Scripture, and the Sacred Magisterium.
The Magisterium (from the Latin, magister, "teacher") is the teaching office of the Roman Catholic Church. Roman Catholic theology divides the functions of the teaching office of the Church into two categories: the infallible Sacred Magisterium and the non-infallible Ordinary Magisterium. The infallible Sacred Magisterium includes the teachings of papal infallibility, of Ecumenical Councils (traditionally expressed in conciliar canons and decrees), and of the ordinary and universal Magisterium. (Despite its name, the ordinary and universal Magisterium falls under the infallible Sacred Magisterium.)
Examples of infallible papal definitions (and, hence, of teachings of the sacred magisterium) are Pius IX's definition of the Immaculate Conception of Mary, and Pius XII's definition of the Assumption of Mary. Examples of infallible Conciliar decrees include the Council of Trent's decree on justification, and Vatican I's definition of papal infallibility. Examples of infallible teachings of the ordinary and universal Magisterium are harder to point to, since these are not contained in any one specific document, but are the common teachings found among the Bishops dispersed through the world yet united with the Pope.
