Saint Augustine defined sacrament as a visible sign of invisible grace. Later, the definition expanded to a sacrament being an outward sign instituted by Christ to give grace. An even more elaborate definition is that sacraments are perceptible signs, words, and actions, accessible to our human nature. By the action of Christ and the power of the Holy Spirit they make present efficaciously the grace that they signify. Truly the sacraments are efficacious signs of grace, instituted by Christ and entrusted to the Church, by which divine life is dispensed to the believers. The visible rites by which the sacraments are celebrated signify and make present the graces proper to each sacrament. They bear fruit in those who receive them with the required dispositions.The actual number of sacraments has differed over the course of Church history. Most of the main line Christian churches would accept the Sacraments of Initiation, Baptism, Confirmation, and Eucharist. Baptism is the sacrament that one receives as an infant or as an adult, if unbaptized. Baptism is recognized by all the Christian churches that use the ritual formula of "I baptize you (name) in the Name of the Father and of the Son and of the Holy Spirit." Baptism incorporates the individual into a believing community of the church and makes one a member. Baptism is received only once in a lifetime.
The sacrament of Confirmation is a continuation, a ratification or sealing of Baptism. If an individual was baptized as an infant, the individual now speaks for him or herself in preparing for the sacrament of Confirmation. Confirmation helps the individual focus on the missionary dimensions of the baptismal commitment. This sacrament is received by teenagers and adults. Confirmation is only received once in a lifetime.
The third and most important Sacrament of Initiation is Eucharist. This is the preeminent sacrament from which all others have meaning. It is when the community of believers gathers around the table (altar) for the breaking of the bread. The Eucharist is the celebration of Jesus' last supper, when he took bread and wine and gave them to the church as his Body and Blood. This Eucharist is celebrated weekly in some Christian churches.
Some Christian churches have the sacraments of vocation, of which there are two: the Sacrament of Matrimony and the Sacrament of Holy Orders. The Sacrament of Marriage celebrates the free giving of one person to another person, for a lifetime. This is also a reflection of the love of Christ for the church. Sometimes the church is called the bride of Christ. Matrimony celebrates and witnesses the covenant of love between two people. A covenant is always understood as freely given and unearned. The Sacrament of Matrimony should only be celebrated once unless there is a death of a partner. Some Christian churches do allow for a second marriage.
The Sacrament of Holy Orders is for the ordained clergy of a Christian church. It should be seen as a sacrament of service by which some are called by God, through the church, to be the spiritual leaders. Some Christian churches also have the fulfillment of Holy Orders and Deacons, which is the step before being ordained a full clergy person. The Sacrament of Holy Orders is only received once in a lifetime. Some Christian churches also have the sacraments of healing, of which there are two: the Sacrament of Reconciliation or Confession and the Sacrament of the Anointing of the Sick. The Sacrament of Reconciliation or Confession focuses on forgiveness in our life and on our acceptance of that forgiveness, which brings the believer back to spiritual health in the family of God and the community after the individual turned away from God's will. The Sacrament of Reconciliation in some Christian churches can be celebrated weekly. Most would suggest it be received before Christmas and before Easter. Some Christian Churches do not believe an individual needs to celebrate this sacrament with a clergy person but can ask forgiveness directly from God.
The Sacrament of the Anointing of the Sick takes place as the community gathers in faith to pray over and lay hands on those who are sick, because the church, like Christ, desires the health of the whole person. Some Christian churches would celebrate this sacrament once a month or a couple of times a year. Other Christian churches would just have the clergy person anoint the sick person either before going into a hospital or any time a sick person wants to receive this sacrament. Not all Christian churches have the Sacrament of Anointing of the Sick.
Over the course of church history, the exact number of sacraments has changed, depending on the particular insights of the believers and the church leadership. In some centuries the sacrament of Holy Orders was three in number: Deacon, Priest, and Bishop. In other centuries the Church itself was considered a sacrament.
Sacraments are more than just a magical number of ritual acts that give grace. They are profound opportunities for people already in God's grace to gather and celebrate that fact through symbolic action and ritual. Sacraments do not happen in church so much as they happen in people who come together as "Church" to celebrate what has already been happening to them. Most of the Christian churches would say that Jesus Christ gave or instituted the sacraments for the people of God, that is, members of the Church.
Sacraments do not begin or end with church leaders or liturgical celebrations. They begin with God's love and care through Jesus Christ to believers. Over time the exact style and method of celebrating a sacrament may indeed change. Because the Church is always changing, sacraments do not end. As long as the Church continues to live and celebrate the sacraments, sacraments will be ongoing symbols of God's loving care.
Yes, sacraments are the visible signs of invisible grace. They are outward signs instituted by Christ to give grace. They are the life of the Church and much more.