The long build up to Easter is called Lent. The day before Lent begins is called Shrove Tuesday. 'Shrove' means being forgiven for wrong-doings. It happens on a different date each year depending on when Easter is. This year Shrove Tuesday is on 28 February, 2017.
Another name for Shrove Tuesday is Pancake Day.
Many people make pancakes on Shrove Tuesday and in some parts of the UK run in pancake races.