The Sacrament of Anointing of the Sick is one of the 2 Sacraments of Healing.
It is intended to strengthen those who are being tried by illness. Illness and sufferings are problems we all face because it makes us realise that we are limited and powerless and we will all die someday. Often Jesus asked the sick to believe and he makes use of different signs in healing: spittle, laying of hands, mud and washing.
In the past, the Sacrament of Anointing of the Sick is called Extreme Unction which means Final Anointing and was given to those at the point of death. However, after Vatican II, it was established that this Sacrament can also be given to those who are seriously ill or in old age.
Only priests and bishops can administer this Sacrament by anointing the sick person with Oil of the Sick. If possible, the sick person should receive the Sacrament of Reconciliation, followed by Anointing and the Eucharist.
The graces of this Sacrament are 1) the uniting of the sick person to the passion of Christ for his own good and the good of the Church, 2) strengthening, peace and courage to endure the sufferings of illness or old age, 3) forgiveness of sins through the Sacrament of Reconciliation, 4) the restoration of health if is conductive to the salvation of his soul, and 5) the passing over to eternal life.
The matter (visible sign) is oil.
The form (words) are "Through this holy anointing, may the Lord in his love and mercy help you with the grace of the Holy Spirit." and "May the Lord who frees you from sin save you and raise you up. Amen."