From the Catechism of the Catholic Church, Simplified
The Seven Sacraments (1113)
The Church has seven sacraments: Baptism, Confirmation, Eucharist, Penance, Anointing of the Sick, Holy Orders and Matrimony. First, we will discuss what is common in their doctrinal aspects, then what is common in their celebration, and finally, what is distinctive about each sacrament.
All Initiated by Christ (1114-1116)
The Council of Trent, "adhering to the teaching of Scripture, to the Apostolic Traditions and to the consensus of the Fathers," professed that "the sacraments of the new law were... all instituted by Jesus Christ, our Lord."
Jesus' words and actions had saving power and anticipated the power of his death and Resurrection. These powerful mysteries are now dispensed in the Church's sacraments. "What was visible in our Savior has passed over into his mysteries" (Pope Leo the Great).
The Church's Treasures (1117-1118)
Through the Spirit, who guides "to all truth" (Jn 16:14), the Church has gradually recognized Christ's treasures and has seen that, among her liturgical celebrations, there are seven (in the strict sense) that are sacraments instituted by Christ.
These sacraments are "by the Church" because she is the sacrament of Christ's actions. They are "for the Church" because they manifest and communicate to men the mystery of God's communion.
The Baptized and the Ordained (1119-1120)
In the sacraments, the Church acts with Christ as "an organically structured priestly community." Through Baptism and Confirmation, people are enabled to celebrate the liturgy. Those who have received Holy Orders are appointed to "nourish the Church... in the name of Christ."
The ministerial priesthood serves the baptismal priesthood by guaranteeing that it is really Christ who acts in the sacraments. The ministerial priesthood is the sacramental bond which links the liturgical action to the apostles' actions and, through them, to Christ's words and actions.
The Seal of Three Sacraments (1121)
These three sacraments (Baptism, Confirmation, and Holy Orders) bestow a "character" or seal which is indelible, remaining forever. By this seal the person is configured with Christ according to the different states in the Church. This seal disposes for grace, guarantees divine protection, and calls the person to worship and service in the Church. These three sacraments can never be repeated.