(NEXSTAR) —  The Lenten season is here for Christians and the unofficial first day has arrived: Fat Tuesday. 

Fat Tuesday – otherwise known by its French name, Mardi Gras – is the last day before Lent begins on March 2, or Ash Wednesday, according to the Christian calendar.

On Ash Wednesday and throughout Lent, Christians “engage in acts of prayer, fasting and almsgiving” for a period of 40 days leading up to Easter, Kim Mandelkow, director of the Office for Worship for the Archdiocese of Milwaukee explained. 

Why 40 days? It commemorates the same amount of time Jesus spent fasting in the desert before starting his public ministry, according to Father Martin Schlag, a professor and chair of Catholic Social Thought at the University of St. Thomas in Minnesota.

As a last hurrah before fasting for the six weeks of Lent, Fat Tuesday is usually marked by celebrations and indulgence. As Mandelkow explains, some use the day as a chance to “clear their homes of any delicious and perishable foods” so as not to waste any while they abstain from meat, dairy, and sugar.

Fr. Schlag also points to fatty foods like eggs, milk, butter, and cheese. In the mid to late 1900s, Christians were instructed to abstain from eggs and dairy products, in addition to meat.

“So no milk, no butter, no cheese,” he explains. “And that’s why on Tuesday, the last day before lent, everybody said, ‘Well, we have to eat all the butter that’s left, and all the cheese that’s left, all the eggs that are left.’ And so that became Fat Tuesday because you had to eat all the fat or it just wasted because you couldn’t keep it for 40 days.”

The Tuesday before Ash Wednesday also goes by another name: Shrove Tuesday. 

During Shrove Tuesday, many Christians participate in confession, burn their palms from the previous Palm Sunday (which is the Sunday before Easter), and finalize their Lenten sacrifice or the penance they’ll practice, like volunteering or praying more.

Outside of the U.S., the name of the day and the foods eaten vary. Mandelkow points to the U.K., where the day is called Pancake Day, and German and Polish communities, which refer to it as Faschnaut Day or Paczki Day, respectively (Both Faschnaut and Paczki are words for doughnut).

So eat your paczki, enjoy your cheese, wear your beads, and prepare for Ash Wednesday’s fast.