In Western Christianity, the feast commemorates principally (but not solely) the visit of the Magi to the Christ Child, and thus Jesus' physical manifestation to the Gentiles. It is sometimes called Three Kings' Day.
It is also known as the Epiphany which is a Christian feast day celebrating the revelation of God incarnate as Jesus Christ.
Three Kings Day is celebrated on January 6 on the 12th day of Christmas.
The Epiphany may have originated in the Greek-speaking eastern half of the Roman Empire as a feast to honor the baptism of Jesus. Around 200, Clement of Alexandria wrote that "But the followers of [the early Christian Gnostic religious teacher Basilides celebrate the day of His Baptism too, spending the previous night in readings.
And they say that it was the 15th of the month Tybi of the 15th year of Tiberius Caesar. And some say that it was observed the 11th of the same month." The Egyptian dates given correspond to January 6.