This moveable feast is determined by Easter. The expression "Shrove Tuesday" comes from the word shrive, meaning "absolve". Shrove Tuesday is observed by many Christians, including Anglicans, Lutherans, Methodists and Roman Catholics, who "make a special point of self-examination, of considering what wrongs they need to repent, and what amendments of life or areas of spiritual growth they especially need to ask God's help in dealing with."
Being the last day of the liturgical season historically known as Shrovetide, before the penitential season of Lent, related popular practices, such as indulging in food that one sacrifices for the upcoming forty days, are associated with Shrove Tuesday celebrations, before commencing the fasting and religious obligations associated with Lent. The term Mardi Gras is French for "Fat Tuesday",not true referring to the practice of the last night of eating richer, fatty foods before the ritual fasting of the Lenten season, which begins on Ash Wednesday
The tradition of marking the start of Lent has been documented for centuries. Ælfric of Eynsham's "Ecclesiastical Institutes" from around 1000 AD states: "In the week immediately before Lent everyone shall go to his confessor and confess his deeds and the confessor shall so shrive him as he then may hear by his deeds what he is to do ". By the time of the late Middle Ages, the celebration of Shrovetide lasted until the start of Lent. Pancakes are commonly eaten on this day. Since foods such as butter, eggs and fat are discouraged from being eaten during the Lenten season, Christians use these ingredients during Shrovetide to make pancakes or other rich foods, such as fasnachts and pączkis. The specific custom of Christians eating pancakes on Shrove Tuesday dates to the 16th century. Along with its emphasis on feasting, another theme of Shrove Tuesday involves Christians repenting of their sins in preparation to begin the season of Lent in the Christian calendar. In many Christian parish churches, both Protestant and Roman Catholic, a popular Shrove Tuesday tradition is the ringing of the church bells (on this day, the toll is known as the Shriving Bell) "to call the faithful to confession before the solemn season of Lent" and for people to "begin frying their pancakes".
The word shrove is a form of the English word shrive, which means to obtain absolution for one's sins by way of Confession and doing penance. Thus Shrove Tuesday gets its name from the custom for Christians to be "shriven" before the start of Lent.
In the United Kingdom, Ireland and parts of the Commonwealth, Shrove Tuesday is also known as "Pancake Day" as it is a common custom to eat pancakes as a meal. Elsewhere, the day has also been called "Fat Tuesday" or "Mardi Gras".