The Solemnity of the Epiphany is what we call it in the Latin Church, in the Eastern traditions it is called "Theophany" and is one of the oldest Christian feast days celebrated - and has, from the earliest dates, been celebrated on January 6th.
Originally Epiphany/Theophany actually celebrated four different feasts: The Baptism of our Lord, the First Miracle of our Lord at Cana, The Nativity of our Lord and the arrival of the "Three Kings" or "Three Wisemen." Eventually in the West, the celebration of the Nativity became the celebration of the Christ Mass, or Christmas, on December 25th. In many parts of the world the tradition of giving gifts, like the Wise Men, is practiced on Epiphany.
Did I mention this is a "solemnity?" Being that this solemnity which falls on a Friday - for all you Catholics who observe Canon Law (which should be ALL of you!) you don't have to offer up your Friday Penance (which traditionally is the abstaining from meat)! Yes, it is STILL a mortal sin to NOT observe SOME sort of penance EVERY FRIDAY THROUGHOUT THE YEAR - EXCEPT when a solemnity falls on a Friday (just as every Sunday is a solemnity, no penance is required on solemnities). Please see the articles I wrote on this earlier (click here or here for another one).