So seeing as Gavin cannot take it on himself to fully explain Shrove Tuesday, otherwise known as "Pancake Day" by the typical masses of the UK population, I devote a genuine journal entry to this topic.
Shrove Tuesday is the day before Ash Wednesday, the date on the Christian calendar that marks the start of Lent. Like other religions (such as Ramadan for Muslims), Lent is a period of fasting to demonstration of faith. In this case Christians emulate Jesus Christ and his resistance to temptation by The Devil. Therefore, 'back in the day' when peoples luxuries were few, the day before Lent began (Shrove Tuesday); they would use up all of their rarest ingredients on making pancakes out of milk, sugar and eggs (not bought mix Burnie), or whatever they had before sugar was a common commodity. With it people would have other items they could afford as a treat. When citrus fruits were uncommon, these were used to flavor the pancakes, creating the current 'traditional' use of lemon juice and sugar. Therefore 'Pancake Day' was born by essentially removing temptation from themselves by having it the day before the fasting period began.
Now that most types of food are widely available in the Western World, fasting is not seen as a challenge for lent as we indulge ourselves regularly in the sweet and exotic. Also, the Christian Faith in the UK has dwindled. People now give up things for Lent such as chocolate or take it upon themselves to improve their life in some way much like a New Years Resolution. But the tradition of 'Pancake Day' has lived on, because people just love to eat for any occasion (Halloween, Christmas, etc.).
Put simply it is like Mardi Gras with pancakes. In a typical Anglican way we probably want to be different from the continent (Europe).
The whole confessing thing was probably just a way of going into Lent absolved of all your sins, to make yourself 'pure'.
Now you know
P.S. I do not consider myself to be an expert in the topic, nor am I affiliated to any religion. My understanding comes from Primary School teachings (school in the UK for children aged 5-11). Therefore discrepancies are likely.