One of the most intriguing parts of the Christmas story is the visit of the Three Kings, Three Wise Men, or Magi, who followed the Star of Bethlehem "from the east" to Judaea to find the Child Jesus, worship him, and give him three symbolic gifts of gold, frankincense and myrrh. They had been asked to pass on information about the Child to Herod, king of Judaea, who knew about prophecies that this baby would challenge his role as King of the Jews.

Warned in a dream that Herod intended to kill the child, the Magi took a different route home to avoid having to give him any information. Herod's reaction was to kill all male babies and young children in Bethlehem - but by that time, forewarned, Mary and Joseph had escaped to Egypt with the child. Who could the Magi have been, and why do Christians continue to remember them? Were they in fact kings?

The word 'Magi' comes from the Greek term for 'priest of Zoroaster'. This connects the three visitors from the East with the ancient Persian prophet and philosopher Zoroaster, whose ideas on searching for the truth and worshipping a god of wisdom formed the religion of ancient Iran. The priests of Zoroaster had an international reputation as astrologers, because the stars were part of their religion.: they were literally 'followers' of stars. Their use of astrology, and their religious practices in general, led to the word 'magus' being applied to the occult. It was also, of course, the root of the word 'magic'.

There is a traditional belief that the Magi came from Persia, which is modern Iran, from Yemen, or from Babylon, which was then a centre of astrology. The only New Testament account of the Magi's visit, in Matthew's Gospel, does not specify that there were three of them: this number was assumed because they were described as bringing three gifts. In Old Testament prophesies, such as Isaiah 60:3, the Messiah is described as being worshipped by kings. This may be one reason why the Magi are described as 'three kings'.

We usually refer to the Magi by the names Caspar, Melchior and Balthasar. These originated from a Greek manuscript probably written around 500 AD in Alexandria, Egypt, and another eighth-century manuscript written in Greek, which probably originated from Ireland. The name of Caspar, which is sometimes given as Gaspar or Jaspar, has been associated with the name of Gondophares, the first-century king who founded the Afghan city of Kandahar and is said to have met St Thomas the Apostle.

In a tradition that began in Armenia, the three Magi have been associated with three different Eastern kingdoms: Caspar with India, Melchior with Persia or modern Iran, and Balthasar with Arabia. The Koran does not mention the visit of the Magi to Jesus, but it was well known in Arabian tradition, and ninth-century Muslim encyclopaedist, al-Tabari, writes of the symbolic importance of their gifts, giving the seventh-century writer Wahb ibn Munabbih as his source.

Their gifts have a symbolic importance for each element of Christ's kingship. Gold is a symbol of kingship on earth, and represents virtue. Frankincense, burnt in Christian religious ceremonies so that its fragrance symbolises the presence of Christ, represents priesthood and prayer. Myrrh was used as an embalming oil and incense in funerals and cremations until the fifteenth century, and is still used to scent anointing oils in the Eastern Orthodox Church. It represents suffering and death, foretelling the way Jesus' earthly life would end.

The Magi do not reappear in the Gospels, but Christian tradition provides some possible stories of what happened to them in later years. There is a story that the apostle Thomas baptised them as Christians on his way to India. Italian explorer Marco Polo claimed that he was shown the tomb of the Magi in the 1270s, at Saveh, south of the city of Tehran. Another tradition has it that St Helena, the mother of the first Christian Roman Emperor Constantine, discovered the remains of the Magi and brought them to the church of St Sophia in Constantinople - ancient Istanbul. It is said that these remains were later moved to Milan, and are now contained within the Shrine of the Three Kings at Cologne Cathedral in Germany, having been sent there in 1164 by Holy Roman Emperor Frederick I.

To this day, the Magi are important to the celebration of Christmas. Their visit to Bethlehem is celebrated particularly by Western Christian churches. The Christian feastday of the Epiphany falls on 6 January. 'Epiphany' means 'appearance' in Greek, and this feastday celebrates the appearance of God in the human form of Jesus Christ. In the West, it concentrates on the visit of the Magi, because this is considered the first time Christ appeared in human form to people who were not Jews. The Magi's behaviour as non-Jewish kings is contrasted with that of Herod the Great.

In the Eastern Christian churches, the Epiphany is a more general celebration of God becoming man. It concentrates on the baptism of the adult Jesus in the River Jordan by John the Baptist, because this was the moment of 'appearance' when he was proclaimed Son of God to the world. However, it also celebrates the other events of Jesus' childhood and youth, from his birth and the visit of the Magi up to the baptism.

Nowadays, especially in Western countries, the Magi are especially celebrated as gift-bringers of Christmas. In Spain and Spanish-speaking areas, children receive their gifts from the Magi, on the night before Epiphany. They leave food out for the three Magi, and also for the camels they use to travel from the East. In the Dominican Republic and Puerto Rico, grass is left out for the camels in boxes under childrens' beds. Each of the Magi is said in Spain to represent a different continent: Caspar Asia, Melchior Europe, and Balthasar Africa. In almost every Spanish city and town, a cabalgata or procession is held on the night of the Epiphany to welcome the Magi, who parade with their servants and throw sweets to the children. The oldest procession of this kind has been happening since 1886 in Alcoy, Spain.

In most parts of Central Europe, the three kings' initials - CMB - are written above the doors of homes to bring New Year blessings for all those inside. 'CMB' also means Christus mansionem benedicat, or 'Christ, bless this house' in Latin. In Austria and Catholic areas of Germany this is done by Sternsinger, or 'star singers', children who dress up as Magi and carry a star, singing Christmas carols. They collect money for charity in return for writing the initials.

In France, Belgium, Spain and Portugal, families share a cake on the Epiphany which contains a small figure of the Child Jesus. Whoever finds the figure in his share of the cake is crowned 'king', or 'queen', for this last day of the holidays, and wears a cardboard crown bought with the cake. This custom is known in France and Belgium as tirer les Rois, or drawing the Kings. In Spain and Portugal, the cake is known as Roscón de Reyes, and is shaped like a ring. Here, too, the person who finds the figure of the Child Jesus in the cake is crowned, but whoever finds the broad bean also baked in the cake has to pay the cost of it to the person who originally bought it. There are similar European-influenced traditions in Mexico, south Texas, Louisiana and New Orleans.