Sacraments are fundamental acts of God's grace. They are holy acts that are performed upon a human being in order to allow him to attain salvation, be adopted into the fellowship of life with God, and be preserved in it. Receiving the three sacraments opens up the possibility for being united with the Lord at the return of Christ.
Salvation in the sacraments is founded upon the incarnation, sacrificial death, and resurrection of Jesus Christ, as well as the sending and activity of the Holy Spirit.
The term "sacrament" is not recorded in the New Testament. The word mysterion which is rendered in some Old Latin Bible translations with the term sacramentum is originally unrelated to the acts that later came to be designated as "sacraments". In antiquity, the term mysterion referred to a secret matter only accessible to the initiated.
According to the Roman understanding, "sacrament" signified, among other things, "pledge of allegiance", "consecration", or "pledge". In the course of the second and third centuries AD, the terms mysterion and sacramentum came to be used in reference to ritual acts. Thus, for example, Tertullian (ca. AD 160-220) associated the baptismal vow and the creed–albeit not the act of baptism itself–with a military oath formulation. The church leader Augustine (AD 354-430) made the most significant contribution to our understanding of the sacraments in later antiquity: a sacrament comes into being through the union of a visible element with a spoken word that refers to the reality behind it.
A sacrament legitimately comes into being through four interrelated variables:
sign (signum/materia), that is the rite or the visible element,
content (res/forma), that is the presence of salvation,
dispenser (the mediator of the sacrament),
faith (on the part of the recipient), so that the sacrament is received for salvation.
The validity of the sacraments is not dependent on their interpretation or the understanding a person has of them, but rather only on the four aforementioned variables. The sign (signum) and content (res) are linked together through the word (verbum) of institution or consecration spoken by the dispenser.
Since this is not a magical or automatic event, as it were, the faith of the person receiving the sacrament is a prerequisite for the sacrament to unfold to its full salvific effect. However, even unbelief does not invalidate the sacrament, because that which God has done cannot be undone by the unbelieving recipient.
The proper administration of the sacraments is incumbent upon the Apostles. They have been commissioned by Christ to make the sacraments accessible in proper fashion. Although not all sacraments need to be dispensed by the Apostles or those commissioned by them, sacraments nevertheless exist in an apostolic relationship.
There are three sacraments (1 John 5: 6-8): Holy Baptism, Holy Sealing, and Holy Communion. They have been instituted by Jesus Christ. 
Through Holy Baptism with water, a human being enters into his first close relationship with God–he becomes a Christian, and through his faith and profession to Christ belongs to the church (see 8.1). Through Holy Sealing, God grants the baptised the gift of the Holy Spirit. Both sacraments together comprise the rebirth out of water and the Spirit. Through this rebirth, a human being becomes a child of God and is called to be numbered among the firstlings at the return of Christ (see 8.3). Holy Communion preserves a human being in the intimate fellowship of life with Jesus Christ. To this end, this sacrament must be received repeatedly in faith (see 8.2).
The sacraments are also dispensed upon children (Matthew 19: 14).
Sacraments are fundamental acts of God's grace. (8)
Salvation in the sacraments is founded upon the incarnation, sacrificial death, and resurrection of Jesus Christ, as well as in the sending and activity of the Holy Spirit. The proper dispensation of the sacraments is the responsibility of the Apostles sent by Christ. (8)
A sacrament comes into being through the union of a visible element with a word that refers to a reality behind this word. (8)
A sacrament comes into being through four interrelated variables: sign, content, dispenser, and faith. (8)
Faith is the prerequisite for a sacrament to unfold to its full salvific effect. (8)
Jesus Christ instituted three sacraments: Holy Baptism with water, Holy Sealing, and Holy Communion. (8)
 cf. Matthew 28: 19-20; John 3: 5; Luke 22: 19-20; John 6: 53-58; 1 Corinthians 11: 23-26; concerning the distinction between Holy Baptism with water and Holy Sealing, see Acts 8: 14-17; 19: 1-6.