The Gospels say that many years before Jesus' birth, prophets had told a promise to the Jewish people that God would send them a Messiah, or holy teacher. Christians believe that the promised Messiah was Jesus. His mother was a young woman called Mary, who was engaged, but not yet married to a carpenter called Joseph. Joseph found out that Mary was pregnant and was upset. He was wondering what he should do, when an angel came from God to tell him that the baby was the Holy One. The angel said that he must name the baby. This was a sign that he would take care of it like his own child.
At this time, the Middle East was ruled by the Romans. An order came that all the people had to travel back to their home town, to put their names on the taxation lists. Joseph took his new wife to Bethlehem. There was nowhere for them to stay, except a stable where the animals slept. This is where the baby was born. Joseph called him Jesus, as the angel had said.
The baby Jesus had two lots of visitors. On the night he was born, angels told some shepherds in the fields that they would find a newborn king lying in an animals' feed bin (or manger). Jesus' other visitors were some wise men who saw a new star in the sky and followed it, until they found the house where the family was now living and gave the young child expensive gifts of gold, incense and a precious herb called myrrh. (The wise men are often traditionally called the Three Kings, because there were three very expensive presents but the Bible does not say how many wise men there were.)
All these parts of the Christmas story are remembered and celebrated in different ways at Christmas: in pictures, songs, plays, stories and in models that are called "cribs", "creches" or "presepe".