Pope John Paul II has been given the Roman Catholic sacrament reserved for the sick and the dying, following the sudden deterioration in his health.
The Pope received the sacrament when he was shot in 1981
However, the ritual, called the Anointing of the Sick, is often misunderstood - it does not necessarily signal that death is imminent.
As well as being given to people at the point of death, it is also given to those who are sick but not in danger of dying - and it can be given more than once.
The Pope has received the sacrament before - after he was shot by a would-be assassin in St Peter's Square in Rome in 1981.
The rite is made up of three parts: the confession of sins and absolution, anointing with holy oil, and finally Holy Communion.
The Catholic Church professes that the rite of anointing the sick with holy oil was instituted by Jesus Christ.
The Apostle St James provided a clear teaching regarding the sacrament in the Bible's New Testament, saying:
"Is any man sick among you? Let him bring in the priests of the Church, and let them pray over him, anointing him with oil in the name of the Lord.
"And the prayer of faith shall save the sick man: and the Lord shall raise him up - and if he be in sins, they shall be forgiven him."
Being anointed with holy oil is a practice referred to frequently in the Bible and occurs in many of the Catholic Church's most holy rites such as baptism, confirmation and ordination into the priesthood.
Head and hands anointed
The oil used in the Anointing of the Sick is usually pressed from olives, but other vegetable oil may be used.
A priest is anointed on the back of the hands not the palms
Called Oleum Infirmorum, the oil is specially blessed by a bishop on Maundy Thursday, the Thursday before Easter, when the Last Supper is commemorated.
In the past the oil was placed on the eyes, ears, nostrils, lips and hands - the parts of the body relating to five senses - as well as the feet and sometimes in the case of men, the loins.
However, in 1972 the rite was simplified so that only the head and hands are anointed.
The priest dips his thumb into the oil and then makes the sign of the Cross on the forehead and palms.
However, in the case of the Pope, the backs of the hands would have been touched with oil, since his palms were already anointed during the ordination sacrament when he first became a priest.
As he places the oil on the forehead the priest says: "Through this holy anointing may the Lord in his love and mercy help you with the grace of the Holy Spirit."
He then anoints the hands with the words: "May the Lord who frees you from sin save you and raise you up."
To conclude the ceremony, if they are physically able, the sick receive Holy Communion - the bread and wine of the Eucharist.
The final Holy Communion, reserved for those in danger of dying, is referred to as Holy Viaticum.
According to Vatican spokesman Joaquin Navarro-Valls, John Paul II received Viaticum on Thursday evening.
However, experts say that given the Pope's recent problems with swallowing and eating it is likely he received only the wine.