The Mass, or Divine Liturgy, is not simply a religious service. The Catholic faith teaches that in each Mass, Christ’s Sacrifice on the Cross is made present. Kneeling (or standing, as Eastern Catholics do) during the consecration of the Eucharist, a Catholic is mystically in the presence of the Crucifixion on Calvary.
An unbroken chain of succession characterizes the hierarchy of the Catholic Church. Christ commissioned the Twelve Apostles, and each one of them in turn commissioned bishops, who in turn ordained other bishops and priests. So every priest and bishop alive today, including the pope and the patriarchs of the Eastern Churches, has a lineage that traces directly back to the Apostles. It is why the Church is known as an “Apostolic Church.”