Paschal Mystery is one of the central concepts of Catholic faith relating to the history of salvation. Its main subject is the passion, death, andthe Resurrection of Jesus Christ – the work God the Father sent his Son to accomplish on earth.
According to the Compendium of the Catechism of the Catholic Church, “The Paschal Mystery of Jesus, which comprises his passion, death, resurrection, and glorification, stands at the center of the Christian faith because God’s saving plan was accomplished once for all by the redemptive death of His Son Jesus Christ.”
The Catechism states that in the liturgy of the Church, which revolves around the seven sacraments, “it is principally his own Paschal mystery that Christ signifies and makes present.”
From Wikipedia.