Boxing Day is a holiday unique to the British Commonwealth. It is a one day holiday on 26th December. Just why and how this holiday came about, you can read here. The history of Boxing Day is fascinating and has nothing to do with the sport of boxing, instead it is a time to continue the Christmas festivities, and includes, of course, food and drink.
After so much cooking on Christmas Day, Boxing Day food continues to be rich and festive but will predominantly be served as more of a buffet, or certainly less formal than the day before.