Authorized service of God in the service of others, according to specified norms revealed by Christ and determined by the Church. In Catholic usage the various forms of ministry include these features: 1. service of God, who is glorified by the loving service given to others; 2. authorization by the Church's hierarchy, whether the Pope directly or the local ordinary; this authorization may require ordination, as in the priestly ministry, or consecration, as in the priestly ministry, or consecration, as in religious life; or liturgical blessing, as with lectors and extraordinary ministers of Holy Communion; 3. based on the teaching of Christ, who showed by word and example how to minister to people's spiritual and temporal needs; and 4. under the guidance of the Church in accordance with her directives and decrees.
"Sacraments are 'powers that comes forth' from the Body of Christ, which is ever-living and life-giving. The are actions of the Holy Spirit at work in his body, the Church. They are 'the masterworks of God' in the new and everlasting covenant." (Catechism of the Catholic Church, #1116)
Sacraments are outward signs of inward grace, instituted by Christ for our sanctification.
The seven sacraments can be drawn together in three categories:
Sacraments of Initiation - Baptism, Confirmation and Holy Eucharist
Sacraments of Healing - Reconciliation and Anointing of the Sick
Sacraments of Vocation - Marriage and Holy Orders