Sacraments are defined as: "outward signs of inward grace, instituted by Christ for our sanctification"
A list of the seven Sacraments are below along with a brief explanation.
In his dialogue with Nicodemus, Jesus taught that Baptism was necessary for salvation. "No one can enter the kingdom of God without being born of water and Spirit" (Jn 3:5). After his Resurrection, Jesus met with the eleven Apostles and gave them the commission to preach the Gospel and baptize, telling them, "Whoever believes and is baptized will be saved" (Mk 16:16).
The word baptism in its origins is Greek and means "immersion" and "bath." Immersion in water is a sign of death and emersion out of the water means new life. To bathe in water is also to undergo cleansing. Saint Paul sums up this truth when he says, "You were buried with him in baptism, in which you were also raised with him through faith in the power of God, who raised him from the dead" (Col 2:12).
The origin and foundation of Christian Baptism is Jesus. Before starting his public ministry, Jesus submitted himself to the baptism given by John the Baptist. The waters did not purify him; he cleansed the waters. "He comes to sanctify the Jordan for our sake . . . to begin a new creation through the Spirit and water" (St. Gregory Nazianzen, Liturgy of the Hours, I, 634).
Jesus' immersion in the water is a sign for all human beings of the need to die to themselves to do God's will. Jesus did not need to be baptized because he was totally faithful to the will of his Father and free from sin. However, he wanted to show his solidarity with human beings in order to reconcile them to the Father.
By commanding his disciples to baptize all nations, he established the means by which people would die to sin—Original and actual—and begin to live a new life with God.
The Sacrament of Penance is an experience of the gift of God's boundless mercy. Not only does it free us from our sins but it also challenges us to have the same kind of compassion and forgiveness for those who sin against us. We are liberated to be forgivers. We obtain new insight into the words of the Prayer of St. Francis: "It is in pardoning that we are pardoned."
Jesus entrusted the ministry of reconciliation to the Church. The Sacrament of Penance is God's gift to us so that any sin committed after Baptism can be forgiven. In confession we have the opportunity to repent and recover the grace of friendship with God. It is a holy moment in which we place ourselves in his presence and honestly acknowledge our sins, especially mortal sins. With absolution, we are reconciled to God and the Church. The Sacrament helps us stay close to the truth that we cannot live without God. "In him we live and move and have our being" (Acts 17:28). While all the Sacraments bring us an experience of the mercy that comes from Christ's dying and rising, it is the Sacrament of Reconciliation that is the unique Sacrament of mercy.
The catechism points out that the Holy Eucharist is both a sacrifice and a sacrament.
As a sacrifice the Holy Eucharist is the Mass. The Mass is that divine action in which Jesus, through the agency of the human priest, changes the bread and wine into His own Body and Blood and continues through time the offering which He made to God on Calvary—the offering of Himself for mankind.
It is at the consecration of the Mass that the sacrament of the Holy Eucharist comes into being. It is then that Jesus becomes present under the appearance of bread and wine. As long as the appearances of bread and wine remain, Jesus remains present and the sacrament of the Holy Eucharist continues to there exist.
The act by which we receive the Holy Eucharist is called Holy Communion.
We might say that the Mass is the "making" of the Holy Eucharist and Holy Communion is the receiving of the Holy Eucharist. In between the two, the sacrament of the Holy Eucharist continues to exist (as in the tabernacle) whether we receive it or not.
Confirmation, together with Baptism and Eucharist, form the Sacraments of Initiation that are all intimately connected. In the Sacrament of Confirmation, the baptized person is "sealed with the gift of the Holy Spirit" and is strengthened for service to the Body of Christ.
The prophets of the Old Testament foretold that God's Spirit would rest upon the Messiah to sustain his mission. Their prophecy was fulfilled when Jesus the Messiah was conceived by the Spirit and born of the Virgin Mary. The Holy Spirit descended on Jesus on the occasion of his baptism by John.
Jesus' entire mission occurred in communion with the Spirit. Before he died, Jesus promised that the Spirit would be given to the Apostles and to the entire Church. After his death, he was raised by the Father in the power of the Spirit.
Those who believed in the Apostles' preaching were baptized and received the Holy Spirit through the laying on of hands. The Apostles baptized believers in water and the Spirit. Then they imparted the special gift of the Spirit through the laying on of hands. "'The imposition of hands is rightly recognized by the Catholic tradition as the origin of the sacrament of Confirmation, which in a certain way perpetuates the grace of Pentecost in the Church'" (CCC, no. 1288, citing Pope Paul VI, Divinae Consortium Naturae, no. 659).
By the second century, Confirmation was also conferred by anointing with holy oil, which came to be called sacred Chrism. "This anointing highlights the name 'Christian,' which means 'anointed' and derives from that of Christ himself whom God 'anointed with the Holy Spirit'" (CCC, no. 1289, citing Acts 10:38).
Sacred Scripture begins with the creation and union of man and woman and ends with "the wedding feast of the Lamb" (Rev 19:7, 9). Scripture often refers to marriage, its origin and purpose, the meaning God gave to it, and its renewal in the covenant made by Jesus with his Church.
God created man and woman out of love and commanded them to imitate his love in their relations with each other. Man and woman were created for each other. "It is not good that the man should be alone. I will make a suitable partner for him. . . . The two of them become one body" (Gn 2:18; 24). Woman and man are equal in human dignity, and in marriage both are united in an unbreakable bond.
Jesus brought to full awareness the divine plan for marriage. In John’s Gospel, Christ’s first miracle occurs at the wedding in Cana. “The Church attaches great importance to Jesus’ presence at the wedding at Cana. She sees in it the confirmation of the goodness of marriage and the proclamation that thenceforth marriage will be an efficacious sign of Christ’s presence” (CCC, no. 1613).
By their marriage, the couple witnesses Christ's spousal love for the Church. One of the Nuptial Blessings in the liturgical celebration of marriage refers to this in saying, "Father, you have made the union of man and wife so holy a mystery that it symbolizes the marriage of Christ and his Church."
The Sacrament of Marriage is a covenant, which is more than a contract. Covenant always expresses a relationship between persons. The marriage covenant refers to the relationship between the husband and wife, a permanent union of persons capable of knowing and loving each other and God. The celebration of marriage is also a liturgical act, appropriately held in a public liturgy at church. Catholics are urged to celebrate their marriage within the Eucharistic Liturgy.
The sacrament of Holy Orders creates a priest.
There's a little more to it than that, of course. As the Catechism's section on Holy Orders says: this "is the sacrament through which the mission entrusted by Christ to his apostles continues to be exercised in the Church until the end of time: thus it is the sacrament of apostolic ministry. It includes three degrees"—the orders of bishop, priest, and deacon. (Catechism, 1536)
But to keep things simple, let's start with the priest.
To know what a priest is we have to know what a sacrifice is.
Nowadays the word "sacrifice" is used in many different ways. But in its strict meaning, its original meaning, a sacrifice is the offering of a gift to God by a group, through the agency of someone who has the right to represent the group.
The purpose of such an offering is to give group worship to God; that is, to acknowledge God's supreme lordship over mankind, to thank him for his blessings, to atone for human sin, and to beg for his benefits.
The Rite of Anointing tells us there is no need to wait until a person is at the point of death to receive the Sacrament. A careful judgment about the serious nature of the illness is sufficient. The Sacrament may be repeated if the sick person recovers after the anointing but becomes ill once again, or if, during the same illness, the person's condition becomes more serious. A person should be anointed before surgery when a dangerous illness is the reason for the intervention (cf. Rite of Anointing, Introduction, nos. 8-10).
Moreover, "old people may be anointed if they are in weak condition even though no dangerous illness is present. Sick children may be anointed if they have sufficient use of reason to be comforted by this sacrament. . . . [The faithful] should be encouraged to ask for the anointing, and, as soon as the time for the anointing comes, to receive it with faith and devotion, not misusing the sacrament by putting it off" (Rite of Anointing, nos. 11, 12, 13).
Only bishops and priests may be ministers of the Sacrament of the Anointing of the Sick. A penitential rite followed by the Liturgy of the Word opens the celebration. Scripture awakens the faith of the sick and family members and friends to pray to Christ for the strength of his Holy Spirit. The priest lays his hands on the head of the sick person. He then proceeds to anoint, with the blessed Oil of the Sick, the forehead and hands of the sick person (in the Roman Rite). He accompanies these acts with the words, "Through this holy anointing may the Lord in his love and mercy help you with the grace of the Holy Spirit. May the Lord who frees you from sin save you and raise you up" (CCC, no. 1513).
For those who are about to depart from this life, the Church offers the person Penance, Anointing of the Sick, and the Eucharist as Viaticum (food for the journey) given at the end of life. These are "the sacraments that prepare for our heavenly homeland" (cf. CCC, no. 1525). These rites are highly valued by Catholics as powerful aids to a good death. Since Holy Communion is the effective sign of Christ's Paschal Mystery, it becomes for the recipient the opportunity to unite one's own suffering and dying to that of Christ with the hope of life eternal with him. The special words proper to Viaticum are added: "May the Lord Jesus protect you and lead you to everlasting life. Amen."