Praised be Jesus and Mary, now and forever.
St. Nicholas was the Bishop of Myra in the first half of the 4th century. He was a saint and died on December 6th in a year between 345 and 352. Besides that, we don't know a lot about his life with certainty, because a full biography wasn't written until the 9th century. It seems he was born about the year 270 in Patara, a port city on the west end of the southern coast of Asia Minor, now in Turkey. St. Paul changed ships in that city on his way to Jerusalem, coming back from his second missionary journey. According to the legend of St. Nicholas, he was an orphan, but he inherited considerable wealth from his parents and used it to help the poor, the sick, and prisoners. Perhaps we can see confirmation of this in a vision that St. Gertrude had. One day she was wrapped in ecstasy and saw the glory that St. Nicholas enjoyed in heaven. The saint confided to her that the Lord has reserved this glory to him because of the great charity he had exercised in his life toward the needy. One story from his legend is of particular importance. A nobleman fell into poverty and so was unable to provide dowries for his three daughters so that they could marry. Lest they be reduced to begging to survive, he decided to prostitute them in order to get money for the dowries. When St. Nicholas heard of this, he decided to save the girls from this terrible fate by secretly throwing three bags of gold coins into their window at night. From this developed the idea of St. Nicholas as someone who secretly leaves gifts and eventually this turned into the popular image of Santa Claus. The legend goes on to say that the Bishop of Myra, seeing his charity and piety, ordained him a priest and this doesn't seem unlikely. If he was a saint, he was certainly charitable and if he became a priest and later a bishop, then he probably showed outstanding virtue. Upon the Bishop's death by the voice of the people, St. Nicholas was called to succeed him. Myra is also on the southern coast of Asia Minor, 40 miles east of Patara. St. Paul also passed through Myra. This is where the escort taking him to Rome for his appeal to Caesar changed ships. They boarded an Egyptian green ship, the one that took them all the way to Malta before it wrecked. Myra was about three and a half miles inland, but it had a port on the coast.
One of the oldest sources for St. Nicholas's life, which dates from around the year 600, relates that St. Nicholas suffered imprisonment for the faith that he courageously confessed during Diocletian's persecution, which began in 303. It also says that in 325 he took part in the ecumenical council of Nicaea. This was the first ecumenical council convoked to decide whether the teaching of Arius was orthodox. Arius said that the son was not God in the same sense that the father is God, that the son had a beginning, he was not eternal. The council condemned this teaching, defining that the son is consubstantial with the father and thus equally God. The story is told that St. Nicholas was so outraged by Arius's heretical teaching that he slapped him. You can imagine the saint who had suffered for the faith being angered by Arius's glib reinvention of it. It's a good story, but unfortunately one that can't be traced back before the late 14th century. In that 14th century version, St. Nicholas strikes on the jaw an Arian.
In the next oldest source from the second half of the 16th century, it's not just any Arian that he hits, but Arius himself, who he slaps rather than strikes on the jaw. Both of these stories are very late. If the story is true, it's hard to explain why it wasn't included in the older biographies of St. Nicholas. Despite the late date of the story, it's a subject for icons and is included in a 17th-century manual of iconography from Mount Athos. The oldest mention of the saint is in a 6th-century document. It tells how he delivered three officials who had been wrongly condemned to death by the Emperor Constantine. The zealous and intrepid bishop died on December 6th in a year between 345 and 352, as I said. He was buried in a mausoleum outside the city, but not forgotten. 
Praised be Jesus and Mary, now and forever.