God's Presence in the World
Christ instituted the sacraments as powers that come forth from him through his ministers and that are performed by the Holy Spirit. Through the sacraments of Baptism and Confirmation, Catholics are entitled to take part in the Church's liturgy (or worship). Ordination is a sacramental bond that ties the priest and the liturgical action to the ministry of the apostles and to Christ. Priests, who are ordained ministers, are there to serve the baptized by administering the sacraments and through celebrating other parts of the liturgy, such as Mass.
Sacraments are known as instruments of faith because through words and symbols they instruct people in the faith, nourishing, strengthening, and expressing it. Through the sacraments, Catholics profess the ancient faith of the apostles. For this reason, the sacramental rites cannot be changed or modified. Not even the highest level of Church authority can arbitrarily change the liturgy.
Baptism, Confirmation, and the Eucharist are called the Sacraments of Christian Initiation. In the early days of the Church, catechumens (or initiates to the faith) received them all at once. These sacraments are the cornerstones of Catholic life: “The faithful are born anew by Baptism, strengthened by Confirmation and in the Eucharist receive the food of eternal life” (Paul VI, AAS 63  657). Penance and the Anointing of the Sick are known as the Sacraments of Healing, and Matrimony and Holy Orders are sometimes called the Sacraments of Commitment.
In addition to grace, the sacraments of Baptism, Confirmation, and Holy Orders confer a sacramental character, or “seal,” upon the believers. The indelible sign of each of these sacraments remains as a promise of divine protection and a call or vocation to worship and service, and it helps the believer be permanently disposed to receiving grace.
Through grace, the sacraments are also instruments of salvation. They are efficacious, because Christ and the Holy Spirit are the ones at work through the sacraments, and they stand as reminders and guarantees of eternal life in God.