The celebration of this sacrament consists essentially in an anointing with oil which may be blessed by the bishop. The anointing is on the forehead and on the hands of the sick person (in the Roman rite) or also on other parts of the body (in the other rites) accompanied by the prayer of the priest who asks for the special grace of this sacrament.
Further reading: CCC 1517-1519, 1531
This sacrament confers a special grace which unites the sick person more intimately to the Passion of Christ for his good and for the good of all the Church. It gives comfort, peace, courage and even the forgiveness of sins if the sick person is not able to make a confession. Sometimes, if it is the will of God, the sacrament even brings about the restoration of physical health. In any case this Anointing prepares the sick person for the journey to the Father's House.
Further reading: CCC 1520-1523, 1532
Viaticum is the Holy Eucharist received by those who are about to leave this earthly life and are preparing for the journey to eternal life. Communion in the body and blood of Christ who died and rose from the dead, received at the moment of passing from this world to the Father, is the seed of eternal life and the power of the resurrection.
Further reading: CCC 1524-1525
