Jesus Christ taught his apostles in a very direct and intimate way, and they in turn were to hand on his teaching faithfully to the entire world. The bishops in union with the successor of St. Peter, the pope, continue to hand on faithfully what Christ taught. This is a "sacred deposit." It is the "doctrine of the faith." This is something received, not made up as we go along. It is for the Holy Father and the bishops who are in union with him by virtue of their apostolic office and adherence to the same teaching which they have received from those who preceded them, to authentically and authoritatively interpret this "sacred deposit of the doctrine of the faith."
The mission of the apostles and their successors is to carry on the mission of Christ the Lord. This mission is nothing other than redemption. To put it clearly and even bluntly: to save souls, to lead people to heaven, and to keep them out of hell. There are two ultimate destinies for every human: heaven or hell. (Purgatory is a final purification; all there are just passing through on their way to heaven.)
Our ultimate abode is a function of free will. "Before man are life and death, whichever he chooses shall be given him" (Sirach 15:17). God has given us an intellect which naturally tends toward truth if we do not impair and destroy its powers through serious sin. "The man who sins becomes a slave of sin," (John 8:34) the Lord Jesus said. The successors of the apostles, the bishops, are charged with the solemn responsibility of saving souls.
The church teaches that the bishops have indeed, by divine institution, taken the place of the apostles as pastors of the church, in such a way what whoever listens to them is listening to Christ, and whoever despises them despises Christ and him who sent Christ (#862; Vatican II, Lumen Gentium 20, 2). It is not a small thing to disobey, or worse, to despise a bishop or the Holy Father. All Catholic Christians must respect, obey and indeed love their bishops and the Holy Father, or they run the real risk of being held in contempt of the One who consecrated and sent these men on mission: the Lord.
It has become all too common today to criticize or condemn the Holy Father and the bishops who are united with him. Even religious and priests are seen at times on national television, or in their respective pulpits, railing against the pope or their own bishop. The faithful should pray for these persons, for they are indeed disoriented spiritually, and on the edge of a precipice. "Whoever despises them (the pope and bishops) despises Christ and him who sent Christ" (#862; Vatican II, Lumen Gentium 20, 2).
The entire church and every member of the church is apostolic. This is so because the church perdures, through the successors of St. Peter, the bishops, in communion of faith and life with her origin; and in that she is sent out into the entire world on the mission of Christ, which is redemption (#863). Every one of us as a baptized Christian must have the Master's interests in mind and at hand. We are each called to work assiduously for the building up of the Kingdom of God. This continually relates back to the mission of salvation for which the "Word became flesh and dwelt among us."
Each of us as "apostles," as persons sent on mission by the Lord through his church, must take seriously the business of being salt and light in the world. Salt not only gives savor to things, it also preserves them from spoiling. One could very easily say that the very fabric of our society, the very fabric of being, is now in danger of rotting due to an apostasy from reality and truth, from goodness and moral ways of thinking and acting. Each of us, in keeping with the apostolic nature of our lives, must be the salt of the earth that prevents the moral decay of the world around us.