St. Catherine's Day is a special day for a lady named Catherine who was very nice and kind. People celebrate it on November 25th every year.
Just like how we celebrate our birthday every year, we celebrate this day in honor of Catherine's kindness and good deeds. People also celebrate it because she was very smart and helped people learn new things.
On this day, people in some countries have a special cake called a "Katarinakakku" or "Catherine Wheel" that is shaped like a wheel. They also have a special parade and wear pretty clothes.
It's a fun day to celebrate and remember a kind and smart lady named Catherine.