Pancake Day is also called Shrove Tuesday and is one last chance for a big party before Lent begins with Ash Wednesday the next day.
Long ago, Christians traditionally used up all the eggs and fat they had in store by making pancakes and feasting on them. This was because when Lent came, they would eat less food, or even fast (do without food sometimes) to help them focus on God and not on the things they wanted. This tradition has been passed down the generations.
Shrove Tuesday always falls 47 days before Easter, a date which changes every year.