Catechism of the Catholic Church

Following this analogy, the first chapter will expound the three sacraments of Christian initiation; the second, the sacraments of healing; and the third, the sacraments at the service of communion and the mission of the faithful. This order, while not the only one possible, does allow one to see that the sacraments form an organic whole in which each particular sacrament has its own vital place. In this organic whole, the Eucharist occupies a unique place as the "Sacrament of sacraments": "all the other sacraments are ordered to it as to their end." (1374) Catechism of the Catholic Church