The Latin word sacramentum means "a sign of the sacred." The seven sacraments are ceremonies that point to what is sacred, significant and important for Christians. They are special occasions for experiencing God's saving presence. That's what theologians mean when they say that sacraments are at the same time signs and instruments of God's grace.
The first sacrament, for all Christians, is Baptism whereby we become a member of the Church and receive the Holy Spirit to help us live as a true disciple of Christ. The other six sacraments (Reconciliation, Eucharist, Confirmation, Marriage, Holy Orders and Anointing of the Sick) are further moments of grace that deepen our Baptismal commitment.