A sacrament is an efficacious sign of grace, instituted by Christ and entrusted to the Church, by which divine life is dispensed to us by the work of the Holy Spirit (CCC, nos. 1131, 774).
The liturgical life of the Catholic Church revolves around the Eucharistic sacrifice and the sacraments. “Worship is integral to our lives as Christians. When we engage in the prayer and ritual of the Church, we are formed as Church. Our sacramental rites are of primary importance while we are gathered.” http://www.catholic.org/prayers/sacrament.php
For general information on sacraments click on the United States Conference of Catholic Bishops web site.