Anointing of the Sick is the sacrament that is received by those who are ill or suffering. By the sacred anointing and the prayer of the priest, the whole Church commends those who are sick to Christ. The sick person receives the Holy Spirit's gifts of strength, faith, peace, and courage, and his or her suffering is united with the suffering of Christ for the building up of the Church. 
Catechism of the Catholic Church [CCC], nos. 1520-23)