We recognize that the Sacraments have a visible and invisible reality, a reality open to all the human senses but grasped in its God-given depths with the eyes of faith. St Augustine, in the 5th century described a sacrament as 'an outward and visible sign of an inward and invisible grace.' It sounds like a very simple answer, but, to understand the depth of what that means, we need to probe rather more deeply. When parents hug their children, for example, the visible reality we see is the hug. The invisible reality the hug conveys is love. We cannot "see" the love the hug expresses, though sometimes we can see its nurturing effect in the child.
The visible reality we see in the Sacraments is their outward expression, the form they take, and the way in which they are administered and received. The invisible reality we cannot "see" is God's grace, his gracious initiative in redeeming us through the death and Resurrection of his Son. His initiative is called grace because it is the free and loving gift by which he offers people a share in his life, and shows us his favor and will for our salvation. Our response to the grace of God's initiative is itself a grace or gift from God by which we can imitate Christ in our daily lives.
The saving words and deeds of Jesus Christ are the foundation of what he would communicate in the Sacraments through the ministers of the Church. St. Francis de Sales said, "The Sacraments are channels through which, so to speak, God descends to us as we through prayer ascend to Him…The effects of the Sacraments are various, although they all have but one and the same aim and object, which is to unite us to God."
St John, in his gospel tells us 'God so loved the world that he gave his only Son, so that everyone who believes in him may not perish but may have eternal life.'(John 3:16) God's love for us, his will for us to participate in his life, is manifested in the Incarnation, God's giving of himself in the humanity of Jesus; 'the word became flesh and lived among us' (John 1:14) Jesus is the visible, outward sign of God's love for us. And, in turn, it is in the Church that Christ remains visible and tangible for us, most particularly in our encounters with him in the sacraments. The sacraments are where we meet Christ, where God's action, in Christ, through the Church, transforms us, bringing us to what God wants us to be. As baptised Christians, this is what we want too, we want to be what God wills for us. And what God wills for us is a life of joy in his presence and the promise of eternity.
The sacraments are "efficacious signs of grace, instituted by Christ and entrusted to the Church, by which divine life is dispensed to us" (CCC 1131). In other words, a sacrament is a sacred and visible sign that is instituted by Jesus to give us grace, an undeserved gift from God. (See also CCC 1084). Christ was present at the inception of all of the sacraments, which He instituted 2,000 years ago. Christ is also present every time each sacrament is celebrated.
Guided by the Holy Spirit, the Church recognizes the existence of Seven Sacraments instituted by the Lord. They are the Sacraments of Initiation (Baptism, Confirmation, the Eucharist), the Sacraments of Healing (Penance and the Anointing of the Sick), and the Sacraments at the Service of Communion (Marriage and Holy Orders). The Catechism of the Catholic Church explains that "the seven sacraments touch all the stages and all important moments of the Christian life" (CCC 1210).
Through the Sacraments, God shares his holiness with us so that we, in turn, can make the world holier. As actions of Christ and the Church, they are signs and means which express and strengthen the faith, render worship to God, and effect the sanctification of humanity and thus contribute in the greatest way to establish, strengthen, and manifest ecclesiastical communion. The Constitution on the Sacred Liturgy tells us, 'The purpose of the sacraments is to sanctify, to build up the Body of Christ and, finally, to worship God. Because they are signs, they also instruct. They not only presuppose faith, but by words and objects they also nourish, strengthen, and express it.'