In order that the full and living Gospel might always be preserved in the Church the Apostles left Bishops as their successors. They gave them their own position of teaching authority. Because the Magisterium of the Church teaches with authority from Christ and with the help of the Holy Spirit, members of the Church are not free to treat this teaching as simply another opinion. Individual bishops, especially diocesan bishops for the people entrusted to them, are to present the truths of the faith which are to be believed and help apply these truths in concrete life situations. This responsibility to pass on revealed truth unchanged and uncorrupted is entrusted to the college of bishops and to individual bishops.
Bishops exercise their responsibility to teach in a variety of ways.
Certainly presiding at sacred liturgy and reflecting within that context on the Word of God is a primary way. They are also charged with supervising and supporting the catechetical effort within their particular Church and also with promoting Catholic schools. Each bishop, as a member of the worldwide college of bishops, also has missionary responsibility. The primary ways that bishops teach together were pointed out above, namely either in an ecumenical council or by the ordinary and universal Magisterium. Bishops can also teach together when gathered in councils properly established or even in conferences of bishops.