Christmas is one of the most important Christian holidays. Catholics, who live mainly in Western Europe, the Americas, Australia, Africa and Asia, celebrate it on December 25.
Christmas is the most important Catholic holiday revolving around the story of how the Virgin Mary gave birth to Jesus Christ, the son of God.
Christmas is preceded by Advent (which lasts between three and four weeks). Advent is a time of strenuous repentance when the faithful go to confession and the clergy don purple robes, the color of repentance.
Each of the church services on the four Advent Sundays have a theme drawn from Evangelical readings: the first is devoted to the coming of Christ at the end of time; the second and third are about transition from the Old to the New Testament, with the third Sunday recalling the mission of John the Baptist; the fourth is devoted to the Gospel events leading up to Christmas.
The Catholic Christmas Eve Mass usually begins at midnight. The hymns sung during the mass are very solemn. By tradition, the priest leading the mass puts the figure of the Christ child in the crib. During the night, at dawn and during the day of December 25 three more special liturgies are celebrated (the bosom of the Father, the loins of the Mother of God and the souls of the believers).
Christmas is celebrated throughout the Christmas Octave, the eight days from December 25 through January 1.
The second day of the festival, December 26, is devoted to St. Stephen, the First Martyr; the third, to apostle and evangelist John the Baptist (on that day wine is consecrated); the fourth day is devoted to the memory of the Holy Infants of Bethlehem (on that day priests offer special blessings to children).
Sunday, which falls on one of the days between December 26 and 31, or, if none of the days is a Sunday in a particular year, December 30 marks the feast of the Holy Family: the Christ child, the Virgin Mary and St. Joseph.
January 1 marks the joy of the Holy Virgin.
Christmas tide continues beyond the Octave until the Baptism of Christ, which in the Roman Catholic calendar is marked on the first Sunday after Epiphany (January 6). Throughout the Christmas holidays the clergy are clad in festive white robes.

Traditions
The Christmas tradition of decorating Christmas trees can be traced back to Germanic peoples in whose rituals the evergreen fir tree was the symbol of life and fertility.
As Christianity spread among the peoples of Central and Northern Europe, the Christmas tree decorated with colored balls acquired a new symbolic meaning: it was put up in homes on December 24, which in Western tradition is Adam and Eve day, to symbolize the tree in the Garden of Eden.
In the context of Christmas, the fir tree symbolizes the tree of the Garden of Eden and the eternal life man acquires through the New Adam, Jesus Christ.
The Gospel narrative of the three Wise Men who came to prostrate themselves before the Christ child and offered him gifts of gold, frankincense and myrrh gave rise to the tradition of exchanging gifts at Christmas. Traditionally the family sits down to a Christmas dinner, with the festive food differing from country to country.
In England, the traditional Christmas meal is roast turkey with gooseberry sauce and Christmas pudding sprinkled with brandy, set on fire and served with the flame flickering.
In the U.S., the Christmas turkey is served with cranberry sauce. In Denmark, they eat a goose or duck stuffed with apples, rice pudding and sweet rice with cinnamon and raisins. In Ireland, they cook turkey or ham, in Greece turkey in wine, and in Lithuania and Germany a roast goose.
Germans put a big plate with apples, nuts, raisins and marzipans on the Christmas table. In China, where a considerable number of Christians reside, the famous Peking Duck is served for Christmas, the favorite dish of Chinese Emperors. 
By contrast, festive dinners in Austria, Hungary and the Balkan countries do not feature goose, duck, chicken or turkey. Eating birds on that day is a bad omen because your fortune may fly away with the birds.
The Belgians eat veal sausage with truffles, wild boar, a traditional cake, and wash it down with wine. In The Netherlands, they have rabbit, deer or other game, and in Luxembourg they eat black pudding, apples and local bubbly.
Italians prefer fish or seafood, tortellini and champagne.
In Spain, they serve a suckling pig roasted on a spit accompanied with sherry. Every Spanish table is sure to be laden with seafood, shrimp, crab, crayfish and Christmas sweets including halva, marzipans and aniseed lozenges.  
The Scandinavians start preparations for Christmas long in advance. Two weeks before the holiday, they slaughter Christmas piglets, make black pudding, and salt and smoke the meat. Finally, they brew beer, a process that goes on non-stop from dawn to dusk for three or four days.

MOSCOW, December 25 (RIA Novosti)