When Jesus Christ came upon the earth and redeemed mankind from sin, He spoke to people personally and extended His graces and blessings to them. He then established His Church to convey His teachings, graces and blessings to future generations. He also established the sacraments as the method by which the graces and blessings of His Redemption would flow to each individual. A sacrament therefore is an outward sign that an individual is receiving grace.
There are three sacraments of Christian initiation; two of healing; and two at the service of communion and the mission of the faithful. Thus, 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". (St. Thomas Aquinas, STh III,65,3.)
The sacraments of Christian initiation — Baptism, Confirmation, and the Eucharist — lay the foundations of every Christian life. The faithful are born anew by Baptism, strengthened by the sacrament of Confirmation, and receive in the Eucharist the food of eternal life. By means of these sacraments of Christian initiation, they thus receive in increasing measure the treasures of the divine life and advance toward the perfection of charity.